Entries in Anaerobic Threshold (6)

Tuesday
Dec062011

Exercise Science and Coaching: Correcting Common Misunderstandings About Endurance Exercise

By: Andrew N. Bosch, PhD
UCT/ MRC Research Unit for Exercise Science and Sports Medicine.
Department of Human Biology, University of Cape Town and Sports Science Institute of South Africa
From: International Journal of Sports Science & Coaching Volume 1 • Number 1 • 2006


Many coaches who work with endurance athletes still believe in old concepts that can no longer be considered correct. Prime amongst these are the understanding, or misunderstanding, of the concepts of maximal oxygen uptake (VO2 max), lactate threshold, training heart rate, and dehydration and fluid requirements during prolonged exercise.

Knowing the VO2 max of an athlete is not particularly useful to the coach, and the exact VO2 max value of any particular athlete can vary considerably as fitness changes. Race performance is a more useful measure on which to base training schedules.

Lactic acid production, far from being an undesirable event, is of great importance and is actually beneficial to the athlete. The lactate concentration during exercise, and the lactate turnpoint, are both widely measured. The nature of the information that these measures can provide about training and training status, however, is still based on information from the 1980s, although more current information is available and many of the original concepts have been modified.

Heart rate is often used to prescribe training intensity, but it is important to understand the limitations inherent in its use. If used correctly, it is a useful tool for the coach.
Similarly, many athletes and coaches still believe that it is necessary to maintain a high fluid intake to avoid dehydration and prevent associated collapse. These beliefs are incorrect, but modern exercise science has been able to advance the knowledge in this area and provide more accurate information.
Exercise science continues to progress and can offer much to the coach willing to accept new and changing ideas.

Key words: Anaerobic threshold; Endurance training; hydration; lactic acid; maximal oxygen uptake; training heart rate

Introduction

Sports science knowledge has progressed tremendously in the last 20 years in terms of the understanding of many of the underlying concepts in exercise physiology and human performance. Many coaches, however, have failed to take cognisance of the new information and still believe in old and out-dated concepts, many of which frankly are wrong. And it is this incorrect understanding that is then applied to the coaching of athletes. In the following article, some of these misconceptions related to endurance performance are highlighted, specifically those around maximal oxygen uptake (VO2 max), lactate threshold, training heart rate, dehydration, and fluid requirements during prolonged exercise. Although runners are most often referred to in the discussion that follows, the principles are applicable to all genre of endurance athlete.

VO2 Max

Every so often a request is received from the coach of a runner or cyclist wanting to know ifit would be possible to measure the VO2 max of one of their athletes. I explain that it is, indeed, possible, but then go on to ask why they want to have the VO2 max of the athlete measured? There is usually one of two replies. Firstly, I am told, by knowing his or her VO2 max the runner will know the esoteric time that he or she is ultimately capable of running for some particular race distance, and therefore their ultimate potential as a runner. Secondly, once their VO2 max is known it will be possible to prescribe the ultimate personalised training schedule. Unfortunately, knowing the VO2 max of a runner does not answer either question.

It is widely believed by those involved in endurance sports that the VO2 max is genetically determined and never changes, and that an individual is born with either a high or low VO2 max. Generally, someone with a high VO2 max value is considered to have a cardiovascular system capable of delivering large amounts of oxygen to the working muscle and is able to exercise at a maximum aerobic work output that is determined by the exercise intensity that can be sustained by this supply of oxygen [1]. In this paradigm it does not appear to matter whether a runner or cyclist is unfit or superbly fit, the VO2 max value obtained in a test is theoretically the same. However, it is intuitively obvious that when fit, the athlete can run much faster on the treadmill than when unfit. Thus, since VO2 max is genetically determined and does not change, VO2 max would be reached at a relatively slow running speed when a runner is unfit compared to when very fit, when a much higher speed or workload can be reached. This means that in a totally unfit world class runner we would measure a high VO2 max (for example, 75 ml/kg/min or higher, a reasonable VO2 max value for an elite runner) at a speed of maybe 17 km/hr in a testing protocol in which the treadmill remains flat during the test. When very fit the same athlete will reach the same VO2 max, but now the speed reached on the treadmill will be around 24 km/hr (a reasonable speed for an elite athlete in such a test). The problem is that such a high VO2 max is never measured at a speed of just 17 km/hr, or thereabout. This would be almost impossibly inefficient [2]. The theory of a genetically set and unchanging VO2 max, regardless of work output therefore begins to appear a little shaky.

This concept of VO2 max evolved originally from misinterpretation of the data of early experimental work [1; 3-5]. It was believed that as an athlete ran faster and faster during a treadmill test, an increasing volume of oxygen was needed by the muscles, a process which continued until the supply of oxygen became limiting, or the ability of the muscle to utilise oxygen was exceeded. At this point there would be no further increase in oxygen uptake, despite further increases in running speed [1]. The plateau in oxygen utilisation was regarded as the VO2 max of the runner. If high, then the athlete had great genetic potential. This has been termed the cardiovascular/ anaerobic model by Noakes [1] and needs revision, although others adhere to the concept [6]. However, 30% of all runners and cyclists tested in exercise laboratories never show a plateau in their oxygen uptake [4; 7]. Instead, the oxygen uptake is still increasing when the athlete cannot continue the test. The conventional view of VO2 max now appears to be even more suspect.

Consider a different possibility. The muscles of a runner require a certain amount of oxygen to sustain contraction at a given speed. When the speed is increased, the muscles have to work harder and there is therefore a corresponding increase in the volume of oxygen needed to run at the higher speed. As the runner runs faster and faster, it follows that there is a concomitant increase in the oxygen required, until ultimately something other than oxygen supply to the muscle prevents the muscle from being able to work harder and to sustain a further increase in running speed.

The brain may be the ultimate subconscious controller, by sensing a pending limitation in the maximum capacity of the coronary blood flow to supply oxygen to the heart as exercise intensity increases, and then preventing a further increase in muscle contractility to prevent damage to the heart during maximal exercise [1].

The volume of oxygen being used by the muscle when maximum running speed has been reached is termed the VO2 max. With this theory, the increase in oxygen requirement merely tracks the increase in running speed, until a peak running speed and therefore peak oxygen requirement (VO2 max) is attained. It is easy to see why the VO2 max value will change (which it does) as a runner gets fitter and becomes capable of running faster. Within this framework, the genetically determined limit of VO2 max is actually determined by the highest running speed that the contractility of the muscles can sustain [8] before the brain limits performance to protect the heart, as described above [1]. Of practical importance, is that the exercise scientist and coach cannot use the VO2 max test as a predictor of future performance in someone who still has the capacity to improve their running by utilising a scientifically designed training programme. A great training-induced increase in running speed will result in a substantial change in VO2 max. Only when widely disparate groups of athletes are tested can a VO2 max value be used to distinguish between athletes (i.e. very fast and very slow [2; 9; 10]). In a group of athletes with similar ability, the VO2 max value cannot distinguish between the faster and slower runners i.e. their race performance. Neither is the knowledge of a VO2 max value going to assist in the construction of a training programme, other than by indirectly giving an indication of the time in which a race may currently be completed, by the use of various tables that are available [11]. Indeed, current race performance provides the most useful information for the coach on which to base training prescription [11].

There are, however, some potential uses of a VO2 max test for a coach. When constructing a training programme for someone who has not run any races and who therefore has no race times from which to determine current ability, a VO2 max test will help by giving an indication of the current capability of the athlete on which to base training schedules. If done at regular intervals, the test can provide information about the efficacy of a training programme [11] as laboratory conditions are very reproducible with regard to temperature and absence of wind. However, the peak speed attained in the test is probably the best indicator of current ability [1; 12-14] and not the actual VO2 max value. Race times remain the most useful measure on which to prescribe running speed in training schedules [11].

Lactic Acid

Most athletes and coaches still believe that lactic acid is released during hard or unaccustomed exercise and that this is what limits performance, as well as being the cause of stiffness. Neither is correct. Furthermore, the terminology “lactic acid,” is not correct.

Lactic acid does not exist as such in the body - it exists as lactate at physiological pH [15], and it is this that is actually measured in the blood when “lactic acid” concentration is measured, as is done when a “lactate threshold” is determined in an athlete. This distinction is important not only for the sake of correctness, but more importantly, because lactate and lactic acid would have different physiological effects.

The first misconception is that lactic acid is the cause of the stiffness felt after an event such as a marathon. Stiffness is due to damage to the muscle [1], and not an accumulation of lactic acid crystals in the muscle [1; 16], as is commonly believed.

The second misconception is that lactate is responsible for acidifying the blood, thereby causing fatigue. To the contrary, the production of lactate is actually important for two reasons. Firstly, when lactate is produced from pyruvate in the muscle, a hydrogen ion is “consumed” in the process [15]. Consequently the production of lactate actually reduces the acidity in the muscle cells and is thus a beneficial process. Secondly, lactate is an important fuel that is used by the muscles during prolonged exercise [17; 18]. It can be produced in one muscle cell and utilized as a fuel in another, or it can be released from the muscle and converted in the liver to glucose, which is then used as an energy source. So rather than cause fatigue, lactate production actually helps to delay fatigue [19].

Anaerobic Threshold

Closely allied to the thinking that lactate production is bad for performance, is the concept of measuring the blood lactate concentration to determine the so-called “anaerobic threshold” or “lactate threshold.”. The origin of this belief can probably be traced to the early studies of Fletcher and Hopkins [20]. Thus we see photographs of athletes at the track or at the side of the pool having a blood sample taken, with an accompanying caption indicating that the workout is being monitored by measuring “lactic acid.” The supposed rationale is that as speed is increased, a point is reached at which there is insufficient oxygen available to the muscle and energy sources that do not require oxygen (oxygen independent pathways, previously termed the anaerobic energy system) then contribute to the energy that is needed. This supposedly results in a disproportionate increase in the blood lactate concentration, a point identified as the “anaerobic” or “oxygen deficient” threshold. This is also known as the lactate threshold or lactate turnpoint.

There are two problems with this concept. First of all, the muscle never becomes anaerobic; there are other reasons for the increase that is measured in blood lactate concentration [21]. Secondly, the so-called disproportionate increase causing a turnpoint is not correct, in that the increase is actually exponential [22-24]. This is seen when many samples are taken, as in the exercise laboratory, where a blood sample can be drawn every 30 seconds as an athlete runs faster and faster.

Although a graph showing a “breakpoint” in lactate concentration as speed increases cannot be drawn as the breakpoint does not exist, a graph can nevertheless be drawn depicting the curvilinear increase in blood lactate concentration as running speed or exercise intensity increases. This curve changes in shape (shifts to the right) as fitness level changes. Particularly, the fitter a runner gets, the more the curve shifts to the right on the graph, meaning that at any given lactate concentration the running speed or work output is higher than before. A shift in the lactate curve to a higher workload or percentage VO2 max occurs due to a reduced rate of lactate production by the muscles and an increased ability of the body to clear the lactate produced [25; 26]. Often, the running speed at a lactate concentration of 4mmol/l is used as a standard for comparison. It is sometimes suggested that this can be used as a guide for training speed (i.e. a runner could do some runs each week at the speed corresponding to the 4mmol/l lactate concentration, some runs above this speed, and recovery runs at a lower speed). Of course, as fitness changes and the curve shifts, these speeds will change, and so a new curve will have to be determined. In concept this works well, but the problem is that neither exercise scientists nor coaches know how much running should be done below, at, and above the 4mmol/l concentration. The 4 mmol/l concentration referred to is a somewhat arbitrarily chosen concentration. It could just as well have been 3.5 mmol/l or 4.5 mmol/l, which would result in different training speeds for the athlete utilizing this system. Indeed, Borch et al [27] suggest 3 mmol/l as the lactate concentration representing an average steady state value. Measuring the maximal steady state lactate concentration may be useful, but requires 4-5 laboratory visits. Thus the real value in determining a ‘lactate curve’ is to monitor how it shifts with training. The desirable shift is one in which a faster running speed is achieved at the same lactate concentration. This regular testing can be done in the laboratory, with the athlete running on a treadmill or on a track, in which running speed can be carefully controlled, such as by means of pace lights.

Training Heart Rate

In recent years the concept of using heart rate while training as an indicator of the correct training intensity, has gained in popularity. Specifically, various heart rate “training zones” have been suggested, and ways to calculate these proposed. This approach has been described in many articles written for coaches and runners [27-29] and does have potential for being a precise way to regulate running intensity in training, particularly for novice runners. However, at present there are no scientific data to support an ideal specific heart rate for different types of training, and much of what is written is based on anecdotal experiences. There is no doubt that future studies will refine this area, making the prescription of training heart rate a more exact science.

Probably the greatest value in heart rate in training is for the coach to use it as a way of ensuring that an athlete does not train too hard on those days when nothing more than an easy training session is prescribed. The use of heart rate for more absolute prescription has the risk of the athlete training at the wrong intensity as a result of the large daily variability in heart rate due to influence of diurnal variation, temperature differences, sleep patterns, and stress [30]. All these can result in the prescribed training heart rate being either too high or too low on a given day. Thus the athlete may train too easily on one day, but on another day when more recovery is needed from a prior hard training session, the training intensity may be too high. The coach is probably better able to assess the most suitable intensity for the athlete. Nevertheless, training intensity based on heart rate may have some value [28].

The use of heart rate as a monitoring tool during training, as opposed to being used to dictate training intensity is a useful aid that coaches can use to assess the training response of an athlete. A progressive decline (over weeks) in heart rate for a given training session would indicate appropriate adaptive response by the athlete; a progressive increase in normal training heart rate would indicate a failure in the adaptive process and that the training load should be adjusted. Similarly, an abnormally high heart rate for a given training session may indicate approaching illness or failure to adapt to the training load and impending overtraining. The athlete would then be well-advised to train only lightly, or to rest [30].

Post-Run Stiffness

In the section on lactic acid, it was stated that the stiffness and muscle pain felt after a marathon or hard workout is not caused by lactic acid. While this was believed to be the case some decades ago, it is now known that lactic acid is not the cause of muscle stiffness, but is the result of damage to the muscle cells, connective tissue and contractile proteins [31-33].

Although the precise cause of delayed onset muscle soreness remains unknown, all runners and coaches are aware that the degree of pain depends on the intensity, duration and type of workout. For example, there is more muscle pain after a long or hard downhill run than after running over flat terrain (i.e. if eccentric muscle actions are emphasised [34]). In fact, it is this phenomenon that begins to exclude a build-up of lactic acid as a cause of the pain. In downhill running, the concentration of lactate in the blood and muscle will be low compared to running at the same speed on the flat. Thus, the most painful post-race stiffness can occur when the lactate concentration is lowest.

If a blood sample is taken from a runner the day after a marathon, especially an ultra- marathon, the concentration of an enzyme, creatine kinase, will be high [35-37]. This is an indication that muscle damage has occurred, as this particular enzyme “leaks” from damaged muscle. The “damage” referred to is minute tears or ruptures of the muscle fibres [38; 39]. This trauma to the muscle can be visualised if a sample of the muscle is examined microscopically. However, it is not just the muscle that is damaged. By measuring the amino acid hydroxyproline, it is possible to show that the connective tissue in and around the muscles is also disrupted [40]. What this shows is that stiffness results from muscle damage and breakdown of connective tissue.

Running fast or running downhill places greater strain on the muscle fibres and connective tissue compared with running on the flat. Downhill running is particularly damaging because of the greater eccentric muscle actions that occur. It is this simultaneous contracting of the muscle while being forced biomechanically to lengthen that is most damaging to muscle fibres.

What does this mean for the runner and coach? From a training and racing point of view, after the muscles have recovered from the damage that caused the stiffness and the adaptive process is complete, the muscle is more resistant to damage from subsequent exercise for up to six weeks [41]. From a coaching point of view, hard training sessions should be withheld when there is muscle pain, as further damage could result. It would be better to allow the appropriate physiological adaptations to take place before resuming hard training sessions. Weight training to increase the strength of the muscle [1] may be beneficial. It has been suggested that vitamin E may help to reduce muscle soreness, but there is little evidence to support this idea [42]. Vitamin E is thought to act as an antioxidant that may blunt the damaging action of free radicals, which attack the cell membrane of the muscle fibre.

It has also been suggested that stretching the painful muscle or muscles may be beneficial, but this has not consistently been shown to alleviate delayed onset muscle soreness. Neither is there any evidence that massage or ultrasound speed up recovery [43]. Similarly, an easy “loosening up” run “to flush out the lactic acid” is unlikely to speed up recovery, although it is also unlikely to result in further damage.

The real cause of muscle stiffness after a hard run is clearly not due to lactic acid in the muscle. Coaches will be in a better position to manage the return to normal training of their athletes after training or racing that has induced muscle soreness, if they understand the effects of type, intensity, and volume of training on muscle stiffness after exercise.

Dehydration, Heat Exhaustion and Heat Stroke

Historically, the understanding has been that runners collapse (most often at the end of races) due to dehydration. This is popularly thought to be more likely when the environmental temperature is high and dehydration more severe. “Heat exhaustion” has been incorrectly thought to be associated with dehydration, yet there is no evidence to support this [1]. “Heat stroke” is an entirely different condition, associated with an increase in body temperature.

There are a number of critical errors in the traditional thinking on the issue of dehydration. Firstly, and possibly most importantly, rectal temperatures are not abnormally elevated in collapsed runners suffering from “dehydration” [44; 45]. Secondly, there is no published evidence that runners with dehydration/ heat exhaustion will develop heat stroke if left untreated [46; 47]. And thirdly, the question must be asked why these runners nearly always collapse at the finish of the race and not during the race. Thus we must look for another explanation as to why the runners collapse.

The explanation is found in a condition called postural hypotension [44; 47-50]. While running, the high heart rate and rhythmic contraction of the leg muscles maintain blood pressure and aids in the return of blood from the legs. When running ceases, the pump action of the leg muscles stops and the heart rate drops rapidly. This results in pooling of the blood in the veins of the lower limb, which in turn causes blood pressure to decrease. It is the lowered blood pressure that results in collapse. Secondly, there is an increase in peripheral blood flow to regulate body temperature. This is more pronounced in hot conditions, and results in a reduction in the pressure of blood filling the heart [51]. Treatment is therefore very simple: If the runner lies down with the legs elevated, the return of blood from the legs is aided, blood pressure is restored and after a short while the runner will have recovered. Cooling the legs may be beneficial. As a preventive measure, it is a good idea to continue to walk after the finish line has been crossed. A second possibility is to lie down as soon as possible and elevate the legs slightly, with cooling of the legs as an additional option.

Heat exhaustion as a result of dehydration does not, therefore, exist and is not a condition that coaches need to be concerned about. This contrasts with heat stroke, in which the body temperature becomes very high (rectal temperature above 41°C) and is a potentially dangerous condition. Even after the athlete has stopped, either voluntarily or because of collapse, the temperature remains elevated because of physiological and biochemical abnormalities in the muscles. Thus the athlete must be cooled as quickly as possible, using methods such as fans, to bring the body temperature down to below 38 degrees Celsius.
Heat stroke develops as a result of a combination of a number of factors. Particularly, a high environmental temperature (>28°C) is more likely to result in the problem than when conditions are cooler. If the humidity is also high, there is an additional heat load on the runner because the sweating mechanism of the body is rendered ineffective. Sweat running off the body, as it does when the humidity is high, does not result in cooling. To cool the surface temperature of the skin, the sweat must evaporate. In addition, and also very importantly, the metabolic heat produced by the runner must be high. Thus, it is the faster athletes who are at risk, who are exercising at a high intensity. It is also, therefore, in races shorter than the marathon in which there is a high likelihood of heat stroke because of the much higher running intensity in shorter races such as cross country (on a hot day) or a 10 km race [46; 47; 52]. Thirdly, it appears that some runners are more susceptible to the development of heat stroke than others [53].

Contrary to popular belief, dehydration is not a major cause of the development of heat stroke. Although adequate fluid replacement during racing in the heat may reduce the risk of heat injury, it is not the only factor and may not even be the most important factor [46; 47; 54; 55]. Arunner can develop heat stroke without being dehydrated. Conversely, a runner can be dehydrated, but not develop heat stroke. If the recommended guidelines for fluid ingestion are followed (~600 ml/ hour), it is very unlikely that fluid deficit will play a role in the development of heat stroke.

Fluid Intake During Exercise

During events such as marathon running, one often reads recommendations suggesting that more than 1L of fluid should be ingested every hour. Ingestion of such a high volume is unnecessary, however, and probably impossible for faster runners to adhere to.

The rate at which fluid ingested during exercise empties from the stomach before being absorbed in the small intestine is influenced by a number of factors. These include the temperature of the fluid, the volume of fluid ingested, and the concentration of any carbohydrate such as glucose, fructose, sucrose or glucose polymer in the water. Thus it is important that athletes follow the correct regimen to ensure optimal fluid and carbohydrate replacement. This consists of ingesting 500-600 ml per hour of a fluid containing 7-10% carbohydrate [56]. This serves two purposes. It supplies a source of carbohydrate to maintain blood glucose concentration, as well as all the fluid replacement that is necessary during prolonged exercise, except possibly under extreme environmental conditions.

Ingestion of too much water during prolonged exercise is not only unnecessary, but can be harmful. In some susceptible people, ingesting large volumes of water can result in a condition called “water intoxication” or hyponatraemia. This occurs when the body’s normal sodium concentration becomes significantly diluted, because the amount of water or sports drink ingested is far in excess of what is needed during exercise to maintain hydration [46; 54; 57; 58]. As with heat stroke, in extreme cases this condition can be life threatening, in this case due to cerebral oedema.

Conclusions

VO2 max testing can be of some limited use to a coach when constructing a training programme for someone who has not run any races. If done regularly, the test can provide information about the efficacy of a training programme. However, the peak speed attained in the test is probably the best indicator of current ability, but race times are the most useful measure on which to prescribe running speed in training schedules.

Rather than cause fatigue, the process of lactate production helps to delay fatigue. In addition, it is important as a fuel substrate. The real value in determining a ‘lactate curve’ is to monitor how it shifts with training, the desirable shift being one in which a faster running speed is achieved at the same lactate concentration.

Heart rate during training is a useful monitoring tool, but should not be used to dictate training intensity. Rather, training heart rate information, together with knowledge of current race speeds and training-induced fatigue, should be used by the coach to determine training intensity. Ultimately, the influence of various parameters that effect heart rate response will be well researched and the coach will then be able to prescribe a specific heart rate for different types of training.

Muscle stiffness after a hard run is not due to lactic acid in the muscle. Return to normal training should be prescribed based on the knowledge that soreness is due to muscle damage.

Dehydration is not a major cause of the development of heat stroke. Heat stroke can occur without dehydration, and conversely, dehydration can occur without heat stroke. If the recommended guidelines for fluid ingestion are followed, it is very unlikely that fluid deficit will play a role in the development of heat stroke.

Ingestion of too much water during prolonged exercise is not only unnecessary, but can be harmful. In some susceptible people, ingesting large volumes of water can result in a condition called “water intoxication” or hyponatraemia.

Despite the exponential increase in knowledge in exercise physiology in the last two decades, the process of exercise physiologists and coaches changing old ideas and concepts and accepting new ones has been slow. Both should examine the new information available and use it to proceed with the next series of research studies and coaching concepts, respectively.

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Friday
Oct072011

Basic Principles for Improving Sports Performance 

By David R. Lamb, Ph.D. Exercise Physiology Laboratory, Sport and Exercise Science Faculty, The Ohio State University, Columbus, OH , Chairman,
Gatorade Sports Science Institute. Print copy: Basic Principles for Improving Sports Performance


Key points

1. For most sports, the top competitor is generally the one who can appropriately sustain the greatest power output to overcome resistance or drag.
2. It is not sufficient for championship performance to simply have the ability to produce great power. The champion must be able to sustain power output in an efficient and skillful manner for the duration of the competition.
3. During maximal exercise lasting a few seconds, the anaerobic breakdown of phosphocreatine and glycogen in muscles can provide energy at rates many times greater than can be supplied by the aerobic breakdown of carbohydrate and fat. However, this high rate of anaerobic energy production cannot be sustained for more than about 20 seconds.
4. For exercise lasting more than a few minutes, an athlete who has a high lactate threshold, that is, one who can produce a large amount of energy aerobically without a major accumulation of lactic acid in the blood, will be better able to sustain a higher rate of energy expenditure than will a competitor who has a lower lactate threshold.
5. A high level of mechanical efficiency, which is the ratio of the mechanical power output to the total energy expended to produce that power, is vital if an athlete is to make the most of his or her sustainable rate of energy expenditure. Mechanical efficiency depends upon the extent to which the athlete can recruit slow-twitch muscle fibers, which are more efficient at converting chemical energy into muscle contraction than are fast-twitch fibers.
6. Neuromuscular skill is also critical to mechanical efficiency because the more skillful athlete will activate only those muscle fibers required to produce the appropriate movements. Extraneous muscle contractions require more energy expenditure but do not contribute to effective power output.

Introduction

The criterion for success in many sports, including those involving running, swimming, bicycling, speed skating, rowing, and cross-country skiing, is simply the time required to propel the athlete's body (and essential equipment such as a bicycle, rowing shell, or skis) for a given distance. In the case of Olympic weightlifting and power lifting, success is determined by how much weight can be lifted in the appropriate movements, whereas a wrestler is judged by the degree of physical control over the opponent. These sports are quite different in terms of the patterns of muscle recruitment, the force and power produced, and the equipment used; nevertheless, success in all of these seemingly diverse sports depends on a complicated application of a simple principle--the champion is the athlete best able to reduce the resistance or drag that must be overcome in competition and best able to sustain an efficient power output to overcome that resistance or drag (Figure 1)(Coyle et al., 1994). This review provides an analysis of the major factors that contribute to an athlete's ability to produce power appropriately to overcome resistance or drag and a number of important applied principles designed to help trainers, coaches, physiologists, and others assist athletes in achieving their goals in sport.


Table 1: mode of the interrelationship of major factors determining sport performance. Performance is determined by how effectively the athlete can sustain sufficient power output to overcome various types of resistance or drag, depending on the sport event. Sustainable power output depends on the rate of energy expenditure that can be sustained throughout the event and the efficiency with which that energy can be converted into mechanical power. Depending on the sport event, sustainable energy expenditure will be a function of the ability to sustain the production of energy by anaerobic and/or aerobic means. Mechanical efficiency is dependent on muscle efficiency, i.e., the efficiency with which muscles convert the energy stored in carbohydrate and fat into muscle shortening, and the neuromuscular skill with which the athlete performs the event, i.e., the degree to which the athlete has learned to recruit only those motor units required to produce maximal power output in a skillful way.

Resistance and drag: Examples in Sport

Examples of resistance in sport include the mass of a barbell in Olympic lifting or power lifting, the muscular efforts of an opponent in wrestling or judo that are used to offset the movements of a competitor, and the effect of gravity on resisting a marathon runner's ability to move up a hill. A lifter who can sustain adequate power output long enough to correctly lift a greater weight than a competitor will beat that competitor. Likewise, a competitor in wrestling or judo who can sustain power sufficient to overcome the resistance provided by the opponent throughout the match will be the winner.

Drag is a special case of resistance in which the friction of air or water around a competitor retards forward motion. Obvious examples of drag are the adverse effects of a headwind on the forward velocity of a competitive cyclist and the retarding effects of water drag on the efforts of a swimmer to move quickly ahead. In cycling on a flat course at speeds greater than 13 km/h (8 mph), most of the resistance to the power generated by a bicyclist is created by the air through which the cyclist's body moves; relatively little bicycling power is lost to friction of the moving components of the bicycle or to the rolling resistance of the contact between the tire and road (Kale, 1991). It is also important to realize that the air drag increases as the square of the velocity of the moving object, i.e., if speed is doubled, the drag increases by four-fold (Kale, 1991).

Air drag offers great resistance in any sport requiring the athlete to move at relatively high velocities; such sports include speed skating--30-40 km/h (19-25 mph) at distances of 0.5-10 km (3-6 mi)--and sprint running--25-35 km/h (15-22 mph) at distances of 100-400 m. In fact, the air creates so much resistance in speed skating that the skaters must assume a tightly crouched posture to reduce their frontal areas exposed to air. Although this posture reduces leg power, it reduces air drag to an even greater extent and thus produces higher skating velocities. Swimmers move at relatively low velocities because they encounter large drag forces from the water as well as from the turbulence at the surface of the water. This drag encountered by a swimmer is not simply a function of body mass, but also of the geometry of the body as it moves through the water.

It is obvious that in events such as bicycling, speed skating, and possibly sprint running, each of which requires the athlete to move through the air at high speeds, the ultimate race time will be determined by the power generated relative to the air resistance. The same is true for the swimmer who must overcome the drag of the water at lower speeds. The main point is that the race velocity in these sports is a function of power production relative to the drag encountered at racing speeds. Therefore, velocity (performance) can be increased by improving power output and/or by reducing drag.

Reducing resistance and drag

In some sports, such as Olympic lifting, power lifting, and the shot put, the very nature of the competition makes it impossible to reduce resistance. If a competitive lifter chooses a low resistance--a lightweight barbell, that athlete is unlikely to win the competition. Likewise, the rules do not allow a shot putter to choose a lightweight shot. However, there are methods that can be used in many sports to reduce resistance or drag. Here are a few examples:
Use Skillful Technique. Competitors in wrestling, judo, rugby, American football, and other "contact" sports can reduce the resistance applied by opponents by skillful misdirection movements that trick the opponents into resisting in the wrong direction. These techniques are learned through many years of practice under the instruction of skillful coaches.

Use Aerodynamic and Hydrodynamic Equipment and Body Postures. In some sports, effective techniques have been employed to reduce resistance and drag in air and water. The designs of golf balls and javelins have become more aerodynamic over the years, and the resulting reductions in air drag have improved the flight characteristics of both. In cycling, riders wear aerodynamic helmets and skintight clothing and assume crouch positions over the handle bars ("aero bars") to minimize wind resistance. In swimming, body position in the water and stroke mechanics are optimized by careful study of underwater videos so that the swimmer reduces water drag as much as possible. Also, engineers have successfully modified the designs of rowing shells, canoes, kayaks, sailboats, oars, and paddles to minimize water drag in competitive events.

Reduce Body Mass. Athletes should carefully consider whether they can effectively reduce resistance or drag by reducing body weight. For pole vaulters, high jumpers, long jumpers, and triple jumpers, gravity is the principal resistance that must be overcome, and body weight is responsible for nearly all of this effect of gravity. Therefore, if these athletes can reduce their body weights without equivalent reductions in their abilities to skillfully generate muscular power, their performances should improve. Of course, if the body weight loss leads to a serious loss of muscular power, performance may well be worsened, not improved. Competing at an effectively low body weight is also critical for distance runners, endurance cyclists, and cross-country skiers. In these sports, the resistance of gravity is a crucial factor in determining performance; in addition, at the higher velocities of cycling, air drag is a major type of resistance that must be overcome, and a smaller frontal body surface area can reduce that resistance.

Weight reduction is not so much of an issue in swimming because the body mass is buoyed up by being immersed in water. However, to the extent that reductions in body weight help reduce water drag, weight loss could be of benefit in swimming, too. Differences in swimmers' individual body builds could play a significant role in determining whether or not weight loss improves swim performance. For example, weight loss may be quite ineffective in a swimmer who already presents a small frontal area and who tends to lose weight mostly in the thighs. However, if a swimmer has exceptionally large shoulders and a large chest, and if the mass of these areas can be reduced effectively through a weight loss program, such an approach could shave time off that swimmer's personal records.

Providing efficient sustained power output to overcome resistance and drag

Power is the ability to apply force through a distance quickly. In other words, power can be thought of as a combination of strength and speed. Interestingly, the sport of power lifting is misnamed because only strength, not speed, is required to be successful; as long as the barbell is moved appropriately, time is of no importance. On the other hand, a person could have exceptionally strong leg muscles and be a pitiful high jumper, sprinter, or long jumper if that strength could not be brought to bear quickly.

Unfortunately, absolute maximal muscular power can be sustained for only a fraction of a second. Thus, assuming equal resistance or drag, the champion in a sport event will not necessarily be the competitor who can produce the greatest maximal power, but instead will be the one who can sustain the greatest power output to overcome the resistance or drag for the duration of the event. This duration may be only a second or two, such as in power lifting, or many hours, such as in an Ironman triathlon.

The ability to sustain a high power output to efficiently overcome resistance or drag involves two major factors--the ability to sustain energy production by the muscles and the ability to apply that muscular energy efficiently to overcome resistance or drag.


Sustaining energy production by the muscles

When energy requirements are extremely high, such as during a sprint in track or swimming or during an Olympic weightlifting event, most of the muscular energy is supplied by two fuels, phosphocreatine (PCr) and glycogen, that are stored in small amounts in the muscles. Because these two fuels can be broken down for energy without the use of oxygen, this is known as anaerobic (without air) energy production. Aerobic energy production occurs at a much slower rate as fats and carbohydrates are broken down with the aid of oxygen in the muscles.

Sustainable Energy Expenditure in Brief, High-Power Events

Brief, high-power activities such as weightlifting and sprinting rely largely on the anaerobic breakdown of PCr and muscle glycogen for energy. When estimates of anaerobic energy production are coupled with simultaneous measurements of aerobic energy production, the approximate relative contributions of these two energy sources during various phases of exercise lasting from 0-180 s are as shown in Table 1. It is clear from the table that the percentage anaerobic contribution to energy production falls off rapidly as the exercise duration increases.

Both PCr degradation and anaerobic glycolysis are activated instantaneously at the onset of high-intensity exercise. Measurements of PCr and lactate from muscle biopsies taken following as little as 1-10 s of electrical stimulation (Hultman & Sjoholm, 1983) and after sprint cycling (Boobis et al., 1982; Gaitanos et al., 1993; Jacobs et al., 1983) confirm the rapid breakdown of PCr and rapid accumulation of lactate. At the onset of less intense exercise, a similar instantaneous activation of both PCr degradation and anaerobic glycolysis occurs but at a much slower rate because the mismatch between energy demand and aerobic supply is reduced during submaximal exertion.

Rate of Anaerobic Energy Production During Exercise

The rate of anaerobic energy provision is critical to success in sports that require the development and short-term maintenance of high power outputs. World-class power lifters and weightlifters can produce power outputs that are 10-20 times that required to elicit the maximal rate of aerobic energy provision, which is estimated by the maximal rate at which the athlete can consume oxygen (VO2max). However, such high power outputs can be maintained for only a fraction of a second. Sprinters can achieve power outputs that are 3-5 times the power output that elicits VO2max, but they can sustain that power output for only about 10 s. However, power output over a 30-40 s sprint can still be sustained at twice the power output at VO2max. Estimates of the rates of anaerobic provision of energy have been calculated from biochemical changes in muscles following intense exercise lasting from 1.3 to 200 s (Spriet, 1994). These studies used non-elite athletes who performed sprint cycling, sprint running, or repeated knee extensions or who underwent electrical stimulation of their muscles. The highest measured rates for energy production from PCr and anaerobic glycolysis during various types of exercise lasting from 1.3-10 s were each approximately 250-500% of the estimated maximal rate of energy provision from aerobic metabolism. In other studies of sprint cycling for 6-10 s, energy production rates from PCr and anaerobic glycolysis combined were about 400-750% of that during maximal aerobic metabolism (Boobis et al., 1982; Jacobs et al., 1983).

The anaerobic energy provision rates decrease when averaged over longer periods of time. In studies that examined intense exercise for 30 s, the average energy provision rate from PCr was about 70-100% of that from maximal aerobic metabolism; anaerobic glycolysis provided energy at a rate estimated to be 220-330% of that from maximal aerobic metabolism (Spriet, 1994). The large decrease in energy produced from PCr when averaged over 30 s, as compared to less than 10 s, indicates that the PCr store becomes depleted between 10 and 30 s of intense exercise. Thus, for maximal exertion lasting longer than about 30 s, it appears that only glycolysis can provide for further anaerobic energy production.

Anaerobic Energy Production During Intermittent High-Power Exercise

Many athletes repeatedly engage in bursts of high-intensity exercise with varying amounts of recovery time between exercise bouts. Examples include a wide receiver in American football, a basketball player in repeated fast break situations, or a swimmer or track athlete during interval training. Most of the energy for short bouts of high-intensity exercise is derived from anaerobic sources; therefore, the ability to recover during rest periods is essential for success in this type of activity. Many studies have examined the performance effects of intermittent high intensity exercise, but few have examined the anaerobic metabolism associated with this type of metabolic stress. Examples of the exercise models that have been studied and provided some conclusions include: 10 bouts of sprint cycling, each lasting 6 s with rest periods of 30 s; four bouts of sprint cycling for 30 s with 4-min rest periods; and two bouts of knee extension exercise to exhaustion in 3 min with 10-60 min of recovery (Bangsbo et al., 1992; Gaitanos et al., 1993; McCartney et al., 1986). Muscle biopsy measurements demonstrated that PCr was decreased by approximately 50% after 6 s and by 75-80% during longer sprints. The PCr is quickly resynthesized during recovery, reaching 50% of rest values by 30-60 s and about 80% by 2-4 min. With repeated sprinting, energy production from anaerobic glycolysis is progressively more difficult to achieve. Presumably, the accumulation of lactic acid in the active muscles plays a major role in the inability to continue producing energy by anaerobic glycolysis. Therefore, after repeated bursts of exercise, PCr is the only potential anaerobic energy source that can be relied upon. However, as described above, it is essential that adequate rest be provided in between intermittent exercise bouts to allow PCr stores to be replenished in the muscles.

Sustained Aerobic Energy Production

The maximal rate of aerobic energy production (VO2max) can be sustained for only about 8-10 min by elite athletes. In events lasting longer than 8-10 min, the best competitor among those with similar values for VO2max is usually the one who can sustain aerobic energy production at the greatest proportion of his or her maximal rate, that is, at the greatest percentage of the VO2max. This in turn is largely dependent on the extent to which the athlete can produce energy aerobically at a high rate without accumulating a large amount of lactic acid in the blood. In other words, the athlete who produces a large amount of lactic acid at a given speed of running, swimming, or cycling cannot continue to perform at that pace for as long as the athlete who does not accumulate as much lactic acid. An athlete who has the ability to exercise at a high intensity before blood lactic acid begins to accumulate is said to have a high lactate threshold (Coyle et al., 1988; Holloszy & Coyle, 1984). An athlete's lactate threshold seems to be a better indicator of endurance performance lasting 30 min to 4 h than does the VO2max (Coyle et al., 1988, 1991).

This is because the lactate threshold is a better index of the athlete's ability to sustain a high rate of energy expenditure for the duration of the competition.

Role of Nutrition in Determining Sustainable Energy Production

Two nutrients, carbohydrate and water, are the dietary constituents that have repeatedly been shown to be most important for optimizing endurance performance. Muscles obviously cannot produce energy without fuels derived from nutrients obtained in the diet, and carbohydrate is an obligatory fuel for high-caliber sport performance. It is well established that dietary carbohydrate consumption before, during, and after exercise can make an important contribution to performance. Carbohydrate consumption acts primarily by increasing the body's stores of glycogen in muscles and in the liver before exercise and by increasing the availability of glucose for use by the muscles during exercise (Coggan & Swanson, 1992; Costill & Hargreaves, 1992; Coyle, 1991; Williams, 1993). Fluid intake during prolonged exercise is also required to counteract the debilitating effects of exercise and heat on cardiovascular function and on body temperature regulation. When dehydration reduces blood volume, oxygen delivery to the muscles by the blood can be compromised, and this reduces the ability of the muscles to produce energy aerobically. Dehydration also compromises the ability of the body to regulate its temperature, resulting in eventual lethargy and potential heat illness, both of which adversely affect the athlete's ability to sustain a high rate of energy production. Carbohydrate-electrolyte beverages are advocated as the most effective way to supply both carbohydrate and fluid to the body during exercise (Coggan & Swanson, 1992; Gisolfi & Duchman, 1992).

Improving the ability to sustain energy production at a high rate

Here are some ways that athletes may be able to improve their abilities to sustain high rates of energy production so they can sustain greater power output to overcome resistance and drag:
At the onset of a training season, the athlete should establish a solid aerobic training foundation by training at relatively low intensities for long durations. This will help develop a greater blood volume, an improved ability of the heart to pump blood, and better networks of capillaries in the trained muscles. These cardiovascular adaptations will lead to an improved delivery of oxygen to the muscles and an enhanced ability of the muscles to sustain high rates of aerobic energy production.

For the bulk of the athlete's training, the specific muscle groups involved in the competitive event should be overloaded, and the athlete should train at a pace or intensity similar to that used in competition (Hickson, 1977, 1985). Such training can lead to improved stores of glycogen and PCr in the trained muscles so that greater energy reserves will be present in the muscles before competition begins. Furthermore, metabolic adaptations to this type of training are likely to enhance the ability of the muscles to utilize fat for energy and to spare muscle glycogen, resulting in less lactic acid production and less accumulation of lactic acid in the blood at a given pace or intensity (Holloszy & Coyle, 1984). This means that the athlete's lactate threshold will be increased so that aerobic energy production can be sustained longer at a greater rate than was possible before training.

During high intensity, anaerobic interval training, the duration of recovery intervals should be sufficient--usually between 30 s and 4 min--to allow the muscles to replenish most of the PCr depleted in the previous exercise interval. If these recovery intervals are too brief, the supply of PCr in the exercising muscles will be inadequate to provide energy anaerobically at a high rate (Gaitanos et al., 1993; McCartney et al., 1986). This means that the athlete will be forced to exercise at a lower intensity (slower pace) and that inappropriate muscle groups may be recruited to accomplish subsequent exercise intervals. If these events occur, the athlete will be learning incorrect movement patterns during training that may adversely affect competitive performance.

The athlete should receive adequate rest--approximately 24 h--between exhaustive training sessions to allow for total replenishment of depleted glycogen stores in the muscles prior to the next training session (Coyle, 1991). Otherwise, the quality of the next training session may be compromised because the athlete's muscles will be easily depleted of one of their main fuels. In addition, training intensity and duration should be gradually reduced during the week before a competitive event so that the athlete's energy reserves are fully loaded before competition.

The athlete should drink plenty of fluids before, during, and after exercise to avoid becoming dehydrated. Dehydration can lead to a diminished ability to deliver oxygen to the muscles, heat cramps, heat exhaustion, and even heat stroke, all of which can impair muscular energy production.

On a daily basis, the athlete should consume a diet high in carbohydrate, about 8 g of carbohydrate per kilogram of body weight (4 g/lb). This will ensure that the muscles can store extra glycogen and may help sustain energy production during competition.

Preliminary evidence suggests that dietary creatine supplementation may increase PCr stores in muscles (Dalsom et al., 1995) and perhaps improve performance in events such as fastbreak basketball that require repeated brief exertions. The extent to which creatine supplementation proves to be useful in actual sport settings remains to be seen.

During prolonged exercise, the athlete should consume carbohydrate-electrolyte drinks containing approximately 6% carbohydrate (glucose, sucrose, or maltodextrins) and a small amount of sodium to help maintain an adequate carbohydrate energy supply to the muscles and to minimize dehydration. Volumes of 150-250 mL (5-8 oz) should be consumed every 15-20 min to replace most, if not all, of the sweat lost by the athlete during exercise (Montain & Coyle, 1992).

Mechanical efficiency: A major determinant of effective power output

Mechanical efficiency for a sporting event is the ratio of the mechanical power output to the total energy expended to produce that power. Typically, both power output and energy expenditure are expressed in watts (W), and the ratio is expressed as a percentage. For example, if a cyclist expends energy at the rate equivalent to 5 L of oxygen per minute (1745 W) to produce 400 W of power on a bicycle ergometer, the mechanical efficiency would be (400/1745) 100 = 23%. Two of the principal factors that determine the mechanical efficiency of an athlete in a sport event are 1) the efficiency with which the active muscles convert the chemical energy stored in carbohydrate and fat to the mechanical energy required to shorten the contractile elements in the muscles, and 2) the neuromuscular skill with which the athlete performs the event.

Role of Muscle Efficiency in Determining Mechanical Efficiency

Muscle efficiency has two components, the first of which is the efficiency with which chemical energy from carbohydrate and fat is converted to adenosine triphosphate (ATP), the only form of chemical energy that can power muscle contraction. The process of ATP synthesis is about 40% efficient, i.e., 40% of the metabolic energy in carbohydrate and fat is transferred into ATP synthesis, whereas 60% of the energy is lost as heat (Kushmerick, 1983; Kushmerick & Davies, 1969). This efficiency of ATP synthesis is fairly constant among individuals.

The second component of muscle efficiency, i.e., the efficiency with which the energy released during ATP hydrolysis is converted to muscle fiber shortening, is more variable than is the efficiency of converting stored fuels to ATP. The efficiency of ATP hydrolysis is dependent on the velocities of muscle contraction (Goldspink, 1978; Kushmerick & Davies, 1969). A peak efficiency of approximately 60% or more can be elicited from myofilaments contracting at one- third of maximal velocity; i.e., the velocity of peak efficiency (Kushmerick, 1983; Kushmerick & Davies, 1969). Thus, slow-twitch muscle fibers obviously have slower velocities of peak efficiency than do fast-twitch fibers (Fitts et al., 1989).

Mechanical efficiency when cycling at 80 rpm is directly related to the percentage of slow- twitch muscle fibers in the vastus lateralis muscles (Coyle et al., 1992). It seems that when cycling at this cadence, the velocity of muscle fiber shortening in the vastus lateralis is close to one-third maximal velocity of the slow-twitch fibers (Coyle et al., 1992). This makes slow-twitch muscle fibers substantially more efficient than fast-twitch muscle fibers at converting ATP into muscular power when cycling at 80 rpm (Coyle et al., 1992; Goldspink, 1978).

Muscle fiber type has a large effect on mechanical efficiency, which in turn has a large influence on sustainable power output as measured during a 60-min bout of cycling in a homogeneous group of cyclists (Horowitz et al., 1994). The cyclists in this study were paired and divided into two groups based upon the percentage (i.e., above or below 56%) of slow-twitch muscle fibers in their vastus lateralis muscles. One group possessed a normal distribution of fiber types, with an average of 48% slow twitch fibers. The other group had 72% slow-twitch fibers on average. These two groups were identical in VO2 max as well as in the VO2 maintained during the ride. Therefore, they possessed the same aerobic energy expenditure potential for this type of task. However, the cyclists with a high percentage of slow-twitch fibers displayed significantly higher mechanical efficiencies and were therefore able to sustain a 9% greater power output (342 W vs. 315 W) during the 60-min ride. Clearly, endurance cycling performance is heavily influenced by mechanical efficiency, which in turn appears to be dependent on the rider's muscle fiber type profile and the efficiency of ATP hydrolysis by the muscle.

Role of Neuromuscular Skill in Determining Mechanical Efficiency

No matter how efficiently one can transform chemical energy into mechanical energy in a given muscle fiber, the overall mechanical efficiency in a sports event will be poor if the athlete is poorly skilled. A good example of the importance of skill is the contrast in the freestyle swimming performances of novice and elite swimmers. The novice may produce a great deal of power, but because the swimmer is so unskillful, the power output is misdirected so that lots of thrashing about occurs with little forward velocity. The elite swimmer, on the other hand, has learned to swim rapidly and gracefully, using only those muscle fibers required to execute the stroke effectively. Neuromuscular skill obviously plays a greater role in determining the mechanical efficiency for some sports, e.g., swimming and wrestling, than it does for others, e.g., running and power lifting, but even small differences in skill can have a major impact on performance in any sport at the elite level.

Improving the athlete's ability to provide power output in an efficient manner

There is little that the athlete can do to improve muscle efficiency because the chemical efficiency of converting fuels to ATP and the proportion of slow-twitch fibers involved in various movements are largely determined by heredity. An exception may be that athletes over many months of training may learn to recruit more of the efficient slow-twitch muscle fibers and fewer of the less efficient fast-twitch fibers. In addition, there are three important steps that can be taken to improve the skill with which power output is applied.

The athlete should obtain the technical advice of competent coaches who can explain how movement patterns should be altered to become more skillful. Often the coach can rely upon personal experience and observation to make critical improvements in an athlete's technique.

Video analysis of the athlete's performance can provide clues about changes in movement patterns that can be made to improve efficiency. The assistance of a sport biomechanist or a coach well-educated in biomechanics could be important in this phase of the athlete's preparation.

The athlete must repeat the appropriate movement patterns in a skillful manner many thousands of times during practice so the nervous system learns to perform the movement correctly every time throughout the entire duration of competition. There is no substitute for skillful repetition of muscular activities to ensure that such activities are likely to remain skillful in the heat of competition.

Summary

For most competitive sports, improving the performance of an athlete can be accomplished by reducing the resistance or drag that must be overcome or by increasing the athlete's ability to sustain a high power output to overcome that resistance or drag. Reducing air resistance or water drag typically involves improving body position in the air or water by minimizing the frontal surface area of the athlete that is exposed to the air or water. Sometimes the apparel or equipment used in the sport, e.g., helmets, swimwear, bicycles, and rowing shells, can be made more aerodynamic or hydrodynamic to reduce resistance or drag.

Increasing sustainable power output requires that the athlete undergo a carefully designed training program that will improve the athlete's abilities to: 1) produce metabolic energy by both aerobic and anaerobic means, 2) sustain aerobic energy production at high levels before lactic acid accumulates excessively in the blood, 3) recruit more of the efficient slow-twitch muscle fibers at exercise intensities used in competition, and 4) become more skillful by recruiting fewer non- essential muscle fibers during competition. Careful attention to maintaining a sufficient intake of fluids and carbohydrate before, during, and after strenuous competition and training sessions is also important.

Although it is apparent that some uniquely gifted athletes are able to win consistently even when their approaches to training are obviously not optimal for reducing resistance or drag and for enhancing their sustainable power outputs, it is clear that such athletes cannot achieve their full potentials in sport without addressing these two basic principles.

* This article was adapted from "Introduction to Physiology and Nutrition for Competitive Sport," by E.F. Coyle, L. Spriet, S. Gregg, and P. Clarkson, which appeared in D.R. Lamb, H.G. Knuttgen, and R. Murray (eds.), Perspectives in Exercise Science and Sports Medicine, Vol. 7: Physiology and Nutrition for Competitive Sport. Carmel, IN: Cooper Publishing Group, 1994, pp. xv-xxxix. The author is especially grateful to Edward Coyle, Ph.D. and Lawrence Spriet, Ph.D. who contributed much of the text for this article.

References

• Bangsbo, J., P.D. Gollnick, T.E. Graham, C. Juel, B. Kiens, M. Mizuno, and B. Saltin (1990). Anaerobic energy production and O2 deficit-debt relationship during exhaustive exercise in humans. J. Physiol. (London) 422:539-559.
• Bangsbo, J., T.E. Graham, B. Kiens, and B. Saltin (1992). Elevated muscle glycogen and anaerobic energy production during exhaustive exercise in man. J. Physiol. (London) 451:205- 227. Boobis, L.H., C. Williams, and S.A. Wooton (1982). Human muscle metabolism during brief maximal exercise (abstract). J. Physiol. (London) 338:21P-22P.
• Coggan, A.R., and S.C. Swanson (1992). Nutritional manipulation before and during endurance exercise: effects on performance. Med. Sci. Sports Exerc. 24:S331-S335.
• Costill, D.L., and M. Hargreaves (1992). Carbohydrate nutrition and fatigue. Sports Med. 13:86-92.
• Costill, D.L., and P.R. Gardetto (1989). Effect of swim exercise training on human muscle fiber function. J. Appl. Physiol. 66:465-475.
• Coyle, E.F. (1991). Timing and methods of increased carbohydrate intake to cope with heavy training, competition and recovery. J. Sports Sci. 9:29-52.
• Coyle, E.F., A.R. Coggan, M.K. Hopper, and T.J. Walters (1988). Determinants of endurance in well trained cyclists. J. Appl. Physiol. 64:2622-2630.
• Coyle, E.F., M.E. Feltner, S.A. Kautz, M.T. Hamilton, S.J. Montain, A.M. Baylor, L.D. Abraham, and G.W. Petrek (1991). Physiological and biomechanical factors associated with elite endurance cycling performance. Med. Sci. Sports Exerc. 23:93-107.
• Coyle, E.F., L.S. Sidossis, J.F. Horowitz, and J.D. Beltz (1992). Cycling efficiency is related to the percentage of Type I muscle fibers. Med. Sci. Sports Exerc. 24:782-788.
• Coyle, E.F., L. Spriet, S. Gregg, and P. Clarkson (1994). Introduction to physiology and nutrition for competitive sport. In D.R. Lamb, H.G. Knuttgen, and R. Murray (eds.) Perspectives in
• Exercise Science and Sports Medicine, Vol. 7: Physiology and Nutrition for Competitive Sport. Carmel, IN: Cooper Publishing Group, 1994, pp. xv-xxxixFitts, R.H.,
• Dalsom, P.D., K. Soderlund, D. Sjodin, and B. Ekblom (1995). Skeletal muscle metabolism during short duration high-intensity exercise: Influence of creatine supplementation. Acta Physiol. Scand. 154:303-310.
• Gaitanos, G.C., C. Williams, L.H. Boobis, and S. Brooks (1993). Human muscle metabolism during intermittent maximal exercise. J. Appl. Physiol. 75:712-719.
• Gisolfi, C.V., and S.M. Duchman (1992). Guidelines for optimal replacement beverages for different athletic events. Med. Sci. Sports Exerc. 24:679-687.
• Goldspink, G. (1978). Energy turnover during contraction of different types of muscle. In: E. Asmussen and K. Jorgensen (eds.) Biomechanics VI-A. Baltimore: University Park Press, pp. 27-39.
• Hickson, R.C., H.A. Bomze, and J.O. Holloszy (1977). Linear increase in aerobic power induced by a strenuous program of endurance exercise. J. Appl. Physiol. 42:372-376.
• Hickson, R.C., C. Foster, M.L. Pollock, T.M. Galassi, and S. Rich (1985). Reduced training intensities and loss of aerobic power, endurance, and cardiac growth. J. Appl. Physiol. 58:492-499. Holloszy, J.O., and E.F. Coyle (1984). Adaptations of skeletal muscle to endurance exercise and their metabolic consequences. J. Appl. Physiol. 56:831-838.
• Horowitz, J.F., L.S. Sidossis, and E.F. Coyle (1994). High efficiency of Type I muscle fibers improves performance. Int. J. Sports Med. 15:152-157.
• Hultman, E., and H. Sjoholm (1983). Substrate availability. In: H.G. Knuttgen, J. A. Vogel, and J. Poortmans (eds.) Biochenistry of Exercise, Vol. 5. Champaign, IL:Human Kinetics, pp. 63-75.
• Jacobs, I., P. Tesch, O. Bar-Or, J. Karlsson, and R. Dotan (1983). Lactate in human skeletal muscle after 10 and 30 s of supramaximal exercise. J. Appl. Physiol. 55:365-367.
• Kushmerick, M.J. (1983). Energetics of muscle contraction. In: L.E. Peachey, R.H. Adrian, and S.R. Geiger (eds.) Handbook of Physiology, Section 10: Skeletal Muscle. Bethesda, MD: American Physiological Society, pp. 189-236.
• Kushmerick, M.J., and R.E. Davies (1969). The chemical energetics of muscle contraction II. The chemistry, efficiency, and power of maximally working sartorius muscle. Proc. R. Soc., Ser. B. 1174:315-353.
• Kyle, C.R. (1991). Ergogenics of bicycling. In: D.R. Lamb and M.H. Williams (eds.) Perspectives in Exercise Science and Sports Medicine, Vol 4: Ergogenics--Enhancement of Performance in Exercise and Sport. Carmel, IN: Brown & Benchmark, pp. 373-413.
• McCartney, N., L.L. Spriet, G.J.F. Heigenhauser, J.M. Kowalchuk, J.R. Sutton, and N.L. Jones (1986). Muscle power and metabolism in maximal intermit-tent exercise. J. Appl. Physiol. 60:1164-1169.
• Montain, S.J., and E.F. Coyle (1992). The influence of graded dehydration on hyperthermia and cardiovascular drift during exercise. J. Appl. Physiol. 73:1340-1350.
• Spriet, L.L. (1994). Anaerobic metabolism during high-intensity exercise (Chapter 1). In: M. Hargreaves (ed.) Exercise Metabolism. Champaign, IL: Human Kinetics (In press).
• Williams, C. (1993). Carbohydrate needs of elite athletes. In: A.P. Simopoulos and K.N. Pavlou (eds.) World Review of Nutrition and Dietetics, Vol. 71: Nutrition and Fitness for Athletes. Basel: Karger, pp. 34-60.

The Gatorade Sports Science Institute® was created to provide current information on developments in exercise science, sports nutrition, and sports medicine and to support the advancement of sports science.


Sunday
Sep182011

Elite Rowing: Maintaining Maximum Condition

By: Dr Richard Godfrey and Greg Whyte
From: Elite Rowing: Maintaining Maximum Condition
 

Dr Richard Godfrey is a Senior Research Lecturer at Brunel University and has previously spent 12 years working as a chief physiologist for the British Olympic Association

Greg Whyte FACSM is director of science and research at the English Institute of Sport


Life at the top – how are elite rowers tested and monitored?

Elite rowers subject their bodies to incredibly high levels of physiological stress. So what kind of testing and monitoring is needed to maintain maximum condition during rowing training without complete breakdown? Richard Godfrey and Greg Whyte explain. 

Olympic rowing events are conducted over a 2,000m course. The event lasts about 320 seconds (s) to 460s, depending upon the number of rowers in the boat and upon competition classification eg heavyweight (now more commonly referred to as ‘open weight’), lightweight, men or women, sculling or rowing. Furthermore, performance, as measured on the water, also depends on external factors, including the environmental conditions ie water temperature, wind speed and direction, and air temperature.
 
The advent of rowing ergometers has facilitated training by providing a controllable and repeatable tool in the assessment of rowing performance. Performance over 2,000m on a rowing ergometer is dependent upon the functional capacity of both the aerobic and anaerobic energy pathways, with the relative amount of energy derived from anaerobic metabolism being 21-30%(1).
 
The study of physiological characteristics of rowers has revealed that power at VO2max, VO2 at lactate threshold (LT), maximum power production and power at a blood lactate of 4mmol.L-1 are the most important predictors of 2,000m rowing ergometer performance in elite rowers(2). (The use of power output at 4mmol·L-1 blood lactate level has been used by a number of coaches and is widely agreed to be important predictor of performance.) However, of the measures listed it is generally agreed that power at VO2max is the strongest aerobic correlate of performance (a finding similar to that seen for endurance running). 

Of the short-term maximal effort tests, maximum force and power production are the strongest correlates of rowing performance. Elite rowers sustain, on average, 77% of maximum power during a 2,000m time trial(1). Thus, if all other determinants remain the same, the greater the maximum power, the greater the average power and resultant speed.
 
The results of ‘off-water’ ergometer studies indicate the importance of higher intensity parameters (power at VO2max and maximum power) in rowing performance. Given this fact, it is perhaps surprising to note that most international teams utilise vast volumes of low intensity training for competition preparation(3). It must be remembered however that sub-maximal economy is important in underpinning power at VO2max, and thus the importance of training that is focused on improving economy and sub-maximal parameters should not be ignored. This type of training typically consists of a number of sessions per week dedicated to lactate threshold training, which has the dual advantage of improving submaximal economy, and improving the power output that can be sustained.

Weight and gender differences

There are significant performance differences between male and female and between heavyweight and lightweight rowers. On the ergometer, researchers have shown that male rowers were on average 7.7% faster than their female counterparts(2). Results from World Championships and World Cup single scull events, suggest that this difference is increased to 10.9% on-water (there are subtle relationships between technique and power delivery which make on-water rowing harder than ergometer rowing, but why the difference is greater between ergometer and on-water rowing in women is not known).
 
The difference between heavyweight and lightweight rowers was 5.5% on-ergometer compared to 4% on-water. While heavyweights are faster than lightweights, research suggests that any increase in body mass should be primarily composed of functional (lean) mass to effect a change in ergometer/boat speed. This is particularly true for lightweight rowers and requires the right combination of diet, rowing-specific ergometer and on-water work, coupled with weight training, which ensures the development of an appropriate functional mass.
 
In describing the physiological components that are necessary for good rowing performance it must be remembered that anthropometric (ie height, limb length), technical (ie stroke length, stroke rate) and psychological factors are also crucial elements of that performance. Assessing the physiological aspects of performance is important in the profiling of athletes, as this allows the design of better training programmes, which in turn improves adaptation.
 
The physiological assessment of the rower should aim to test the range of physiological requirements of rowing performance, both aerobic and anaerobic. The following section outlines the range of tests employed by physiologists to assess elite rowers in laboratory and field (on-water or on ergometers in the boathouse or gym) settings. 

Laboratory testing for rowers

Rowing is a strength-endurance sport with a large aerobic component. A number of endurance sports have been proposed as the ‘most aerobic’, including cross-country skiing and running. But when scaling is used (that is a mathematical technique to allow individuals of different sizes and weights to be compared) then heavyweight rowers come out on top (4,5).
 
Heavyweight rowers are large individuals with an average height of 1.93m and average weight of 93kg. Although their body fat values tend to be slightly higher than their lightweight team-mates, they still carry considerable muscle mass.
 
Elite rowers require the ability to generate moderate to high forces and sustain efforts for six minutes (the average time to complete 2,000m in competition at World Championships or Olympic games). Physiology support in the laboratory is therefore designed to examine the current conditioned state of the individual with respect to body composition, muscle power and force, aerobic power and sustainable percentage of maximal aerobic power.
 
Body composition testing is particularly important for lightweight rowers because they cannot afford to be carrying excess ‘non-functional’ weight (ie body fat).
As mentioned previously, it is important to measure maximal aerobic power (VO2max) and the percentage of maximal aerobic power that can be sustained. To do this the discontinuous incremental protocol (commonly referred to as a ‘step-test to max’ and shown in figure 1) is the usual test used.
 
In the lab, testing occurs on a Concept 2 Model C rowing ergometer, the kind of rowing machine found in most health clubs. There is a difference however, as (unlike the standard rowers) the lab ergometer is also fitted with a special force transducer at the handle, so that the force produced by the rower can be directly and very accurately measured.
 
On this equipment, a test is first carried out to examine strength and power. Before the test begins the rower performs a 10-minute warm-up followed by some light stretching. A specific warm-up is then completed using hard efforts of two, three, and four strokes prior to starting the test. For the test itself, the rower is instructed to carry out seven strokes as hard as possible at a rate of 30 strokes per minute. From this test, work (in joules), mean force (in newtons), mean power (in watts), stroke rate (strokes per minute, spm) and stroke length (in metres) are reported from the last five strokes.
 
Elite rowers are often asked to perform 2,000m time trials on the ergometer in training, and so will have a recent 2,000m time. If a young rower visits the lab for the first time it can be difficult to know what intensity to start the step test at. However, a means of determining this has been devised.
 
The time for 2,000m should be converted into a 500m split time. For heavyweight men and women add 15 seconds to this time and you have the split for the third stage of the step-test. For the power output that equates to the time for stage 3, subtract 25 watts to get the power output (and split time) for stage 2 and subtract 50 watts for stage 1. For stage 4 add 25 watts and for stage 5 add 50 watts. For lightweight men and women, also add 15 seconds to the calculated 500m split time to find the split for the third stage. However, it may be more appropriate to use 15-20 watt increments (rather than a 25 watt increment) to calculate subsequent stage workloads(5).
 
During the step test the rower wears a heart rate monitor and a mouthpiece for collection and analysis of expired air, and every four minutes the rower stops to have an earlobe blood sample taken for blood lactate analysis.
 
The heart rate associated with LT can be used to determine a number of heart rate zones that can be used for training, and, after a few weeks, improvements in endurance are detected as a rightward shift of the lactate curve.
 
For the final stage of testing, the individual is asked to cover the furthest distance possible (at a relatively even pace) in four minutes. Traditionally, laboratory-based blood lactate measuring equipment such as Analox, Yellow Springs or Eppendorf lactate analysers have been preferred, as their validity and reliability has been tested and is well known. Although it is possible to use new ‘palm top’ lactate analysers, their validity and reliability continue to be questioned.
 
The data collected and calculated from the step test includes VO2max, power at VO2max, the percentage of maximum that can be sustained (ie at lactate threshold as a percentage of VO2max), power at LT and power at reference blood lactate vales of 2 and 4mmol.L-1

Field-testing for rowers

Many elite sports routinely enjoy a physiology support programme and hence, coaches and athletes have greater experience of sports science. As a result, coaches in many sports are increasingly demanding that field-based testing replace laboratory-based testing. However, coaches and athletes rarely have the training and experience of professional sports scientists and, while many physiologists are not averse to an increase in the use of field-testing, it is very difficult to justify the elimination of laboratory-based testing altogether.
 
Laboratory-based testing provides an objective set of data collected under standardised conditions(5). This level of standardisation and objectivity could never be achieved in the field. However, field-based data has greater sports specificity, something which is very difficult, or is impossible, to achieve in a laboratory-based simulation of the sport. Accordingly, GB elite rowers are still lab tested two to three times per year with 4-5 field-based (step-test) sessions. To supplement this, the coach also carries out some performance tests such as, 18km, 30minute, 2km or 250m rows. On some occasions blood samples can be taken (by a physiologist) at the end of such rows, or the 18km row can be broken into 3 x 6km rows with a 30-60 second rest interval for blood samples to be taken.
 
At field camps overseas, early morning monitoring is routinely carried out prior to daily training. This involves the measurement of urine concentration to monitor hydration status, blood urea, body mass and resting heart rate to examine how the athlete is coping with the physical stress of exposure to a new, often extreme, environment, coupled with normal training. All of these measures are viewed in combination with a psychological inventory and some discussion with the coach and athlete. As a result, the coach decides on whether any modification of training is required for certain individuals as a consequence of this plus on-water and gym-based data.

Altitude camps

Originating in Eastern Europe, the use of altitude training camps in rowing has become commonplace. Elite rowers may ascend to altitude for training camps lasting up to 3 weeks on as many as three occasions per year. Altitude results in a lower availability of oxygen to the working muscles, due to lower barometric pressures, and this reduced availability of oxygen results in an increased physiological stress both at rest and during exercise.
 
The primary purpose of altitude training is to capitalise on the adaptations associated with this increased physiological stress, which is suggested to increase red cell mass and haemoglobin concentration and hence, increase oxygen carrying capacity.
 
Unfortunately, these adaptations come at a price; altitude has a number of undesirable effects that can affect the health and performance of the rower including; sleep disturbance, dehydration, glycogen depletion, immune suppression and an increased incidence of illness including upper respiratory tract infections and gastrointestinal upsets. Altitude training can even lead to a reduction in performance due to a relative deconditioning associated with an enforced lowering of training intensity(6).
 
It is for these reasons that monitoring rowers at altitude is crucial to optimise the beneficial effects and reduce the adverse effects of low oxygen availability. Physiological monitoring of the rower at altitude is based upon assessing sleep quality, recovery, hydration and training intensities. Recent advances in the simulation of high altitude environments at sea level by reducing partial oxygen pressure (ie reduced O2 concentration) in chambers, tents and face masks has led to new opportunities in the use of hypoxia (low oxygen) for training and competition(6).

Summary

The functional capacities of the aerobic and anaerobic energy systems are important in 2,000m rowing, and performance and power at VO2max, VO2 at lactate threshold, power at a blood lactate of 4mmol.L-1 and maximum power production are the most important predictors of 2,000m rowing ergometer performance in elite rowers. Laboratory-based testing is centred on step and maximum power tests and body composition assessment, while field-testing includes ‘on-water’ tests such as 18km, 30minute, 2km or 250m rows and lactate measurement following set pieces.
 


Wednesday
Sep072011

Training The Energy Systems

By Dr. Fritz Hagerman

PDF link: Training the energy system.


Dr Fritz Hagerman: Background

Dr. Fritz Hagerman, a world-renowned expert in exercise physiology, has been educating and improving rowers and coaches for over 30 years. Fritz's groundbreaking research in rowing physiology began in the late 60s with New Zealand's National team, and he has continuously worked with the U.S. National team since 1972. The results of his research have positively impacted the performance of our national teams by teaching athletes how to improve their training regimens as well as helping coaches to identify those with the best physiological potential. He has been working closely with U.S. Men's Coach Mike Teti since 1997. Fritz is a Professor of Physiology at Ohio University and also serves as the Head of FISA's Sports Medicine Commission. irow.com is extremely honored to have "THE MAN" in rowing physiology share his knowledge with us.

TRAINING THE ENERGY SYSTEMS: Part I

It was emphasized in "Defining the Energy Systems" that the interaction among the three energy systems - ATP-PC and Lactic Acid Systems (anaerobic), and the Oxygen System (aerobic) - during rowing training and competition represents several complex biochemical processes. It should, therefore, be of no surprise to any of our previous or more recent on-line viewers to learn that it is difficult to blend these three systems into an effective training program that will maximize the use and development of each system and result in improved rowing performance.

Before discussing specific recommendations to improve the effectiveness of each energy system, it is important to review the basic principles of training. Training should be mostly task specific, and when not rowing, the athlete should exercise to simulate the rowing stroke, whether in part or as a whole, including resistance or weight training.

The only exceptions would be off-season cross-training or alternative training due to an injury caused or aggravated by rowing. Overload the physiological systems, but don’t concentrate this overload; follow the 10% rule when starting a training program, meaning an increase of no more than 10% per week in training frequency, duration, and intensity. As training progresses, then the weekly increase can be reduced to as low as 5%.

Also, don’t forget that rest and recovery are vital ingredients in the best training recipe; a failure to plan for these can produce disastrous results, including peaking at the wrong time, overtraining, or chronic fatigue. Remember, under-training is usually never a problem for the motivated rower. If you are unusually tired, injured, or sick, then taking a day or two off should not be considered a serious training set-back.

Instead, abstinence of training under any of these conditions is a wise choice. Because most interruptions of training are due to respiratory infections, it is recommended that training be reduced if the respiratory problem is above the neck and cancelled if it is below the neck.

Consistency of training is one of the most important training principles; you must use it, or lose it, and as you know, it is far easier to maintain a highly trained state than to achieve one. Individualize your training program based on your skill and fitness levels, availability of training facilities and equipment, and the amount of time you have available. There is no "best time" of the day to train, as it has been shown conclusively that the body doesn’t "care" when you decide to train. However, very early morning time (1-4am) and training immediately before bedtime or following a large meal should be avoided. An increase in training should also be accompanied by an increase in the quantity and quality of food intake, a higher intake of calories will be necessary to fuel the energy systems.

Part II: Peaking

Probably the most difficult job for any coach or self-trained athlete is to design a training program that will permit “peaking” at the right time. This goal is sometimes further complicated by the need to “peak” more than once in a period of only a few months which is often the case of U.S. Olympic qualifiers.

Successful and competitive performances are dependent on carefully planned comprehensive training programs that usually span several weeks or months including up to a year or more. Periodicity of training provides planning for long-term periods (macrocycles) which, in turn, are divided into number of training sessions, days, or weeks (microcycles).

Macrocycles are often represented by an out-of-competition period, a preparation period, and a competitive period and for rowers who live north of the equator, these periods would include approximately September through December, January through April, and May through August respectively. Furthermore, training can be categorized as either specific or non-specific. Specific training includes all work done on the water, rowing ergometry, and tank exercises whereas non-specific (supplemental) training can include weight training, flexibility exercises, or any form of cross training such as cycling, swimming, running, or cross country skiing.

A well-planned training program is based on four specific training factors: type of training (specific and non-specific), frequency (number of sessions per day, week, or cycle), duration (length of time for each training session), and intensity of training (rate of doing work). The intensity of work is the most critical factor in planning a program which will culminate in your best performance. It is well known that the timing of increasing or decreasing intensity determines whether an athlete “peaks” at the desired time or not. In addition, if intensity is increased at too high a rate it can lead to overtraining, injury, and fatigue. The selection of the right mixture of the four training factors is the basis of successful conditioning.

As you train it is good advice to learn and remember how the body responds to exercise and as you plan a training schedule, record it (computer, audio, or written); don’t go on the water, enter the weight room, or sit on the ergometer without a plan. When you complete each training session, again record what you have done, compare the results with your intended plan, and immediately note how your body reacted to the training session. Modifying or changing training programs may be necessary and comparing your specific training regimens with your competitive performances over time will permit you to more objectively make accurate modifications.

Part III: The ATP-PC System

Although certain training recommendations will tend to benefit one energy system more than another, their close relationship insures an energy continuum. Despite emphasizing one energy system with a specific training stimulus, it is likely you will always have some overlap among systems, especially when you consider the variable time frames and weather conditions in which rowing, training, and competition take place.

It is also important to point out that there are a number of different ways to train each of the energy systems and a wealth of training information is now available in several different forms; video and audio tapes, the internet, live symposia, and the old stand-by, the written word. If anything, hopefully the information presented here will help you to make better and more intelligent training choices.

You may recall the description of the three energy systems available to the rowing muscles from the previous presentation on this website; the ATP-PC System, the Lactic Acid System, and the Oxygen System. With the exception of the few seconds of an exercise when our muscles must rely on the ATP-PC System for energy, the use of the other energy systems depends on the duration and intensity of the exercise.

The Adenosine Triphosphate-Phosphocreatine (ATP-PC) System

Because of only a limited contribution of this system to rowing and because it is used most effectively during the first few seconds of any exercise, it is not necessary to devote much of your training time, if any, to the improvement of this system. Our earlier research indicated that this system contributes less than 5% of the energy needed to row a highly competitive 2000m race.

Recent research seems to tell us that insignificant changes occur in this system despite regular performance of high intensity bouts of exercise that last between 5 and 15 seconds. If you want to train the ATP-PC System, it is suggested that multiple intermittent work bouts of less than 20 seconds be performed, e.g., racing starts, with recovery periods of 40-60 seconds between each work bout. In this way the work bouts are too brief to provide much stimulation to anaerobic glycolysis (Lactic Acid System), and the relative long recovery periods permit adequate restoration of ATP and PC. This also means less lactic acid is produced, thus lowering the prospect of acute fatigue associated with this by-product of anaerobic metabolism. Training at or greater than 100% of maximum effort (see accompanying training intensity table) will stimulate this energy system.

Although some athletes appear to be blessed with more powerful ATP-PC systems, the quickness and explosiveness of a rower are also determined by other factors such as muscle fibre type distribution and complex neuromuscular relationships. There is no difference in the biochemical machinery of this system between men and women, however, men tend to have higher absolute energy outputs because of their larger skeletal muscle mass. To suggest that a rower cannot get faster or react more quickly, with training, is incorrect, but it would be more productive to concentrate on developing skill and technique at higher velocities than attempting to design training sessions concentrating solely on improvement of the ATP-PC System.

It is interesting to note that probably the most widely used ergogenic aid in sports today is phosphocreatine (PC). This compound has gained popularity because it is not found as part of any sports federation banned or illegal substance list, it is suggested to be effective in improving performance, and, at least for now, there appears to be no known acute or chronic side effects. If PC is effective, then it would be for only short periods. A recent avalanche of reports concerning PC has tumbled out of both the scientific and non-scientific communities, and the results are equivocal.

Although short bouts of repetitive muscular efforts have been shown to improve using isolated muscle groups as a result of PC ingestion, sports performances following PC use, both actual and simulated, are less impressive. There seems to be a strong relationship between the amount of PC stored in the working muscle and the ability to perform repetitive anaerobic work bouts, but it is difficult to assess the PC storage capacity or content of muscle and this capacity and content apparently vary from one individual to the next. PC may be similar to our electrolyte use; if we are low in calcium then exercise performance may be impaired.

However, it would be unwise to simply consume large amounts of calcium without knowing what its concentration is in the body; calcium is relatively easy to measure in the body, PC is not. There are also no reports of the long-term effects of PC use and it will be some time before these data are available. Although the distributors of PC are recommending that all sports will benefit from its use, there is no reliable evidence that this is the case and nor is there valid evidence that increased muscular concentrations of PC spare or delay the use of the other energy systems, thus contributing to a possible larger and more efficient energy pool.

Part IV: Anaerobic Glycolysis – Lactic Acid System (LAS)

Although this energy system accounts for only about 15 to 20% of the energy contribution during a 2000m race, the timing of its contribution is critical. Because elite rowers generate their highest power outputs in the first 500m of a race, significant amounts of lactic acid are produced during the first 90 seconds. In fact, our research has shown that blood lactate concentrations reach maximal levels within the first 2 minutes of a 2000m race.

Therefore, the rower usually tolerates a very high lactate load for an additional 3-4 minutes until the sprint, when the Lactic Acid System is once again challenged to make a significant energy contribution. Venous blood lactate values in excess of 20 mmol/L of blood have been observed for elite rowers following 2000m competitive efforts and, when compared with responses of elite aerobic athletes in other sports, the rower’s responses have been among the highest. As a result, one can appreciate the physical discomfort a rower experiences during and immediately following a race.

It is important to note that measuring blood lactate does not reflect the total amount of lactate produced by the working muscles. Instead it is more of a residual concentration of lactate left over following a complex series of biochemical cellular reactions that involve lactate production, transport, clearance, buffering and resynthesis to ATP and glycogen. Maximal lactate concentrations are quite variable among individuals, but tend to be more consistent following sub maximal efforts. The Lactic Acid System’s (LAS) range of maximum energy production is 60-90 seconds during high intensity exercise.

Although there are several training schemes designed to improve this energy system, it is recommended that any training intensity above anaerobic threshold (AT) will improve the LA System (see intensity table). There is also evidence to indicate that this system, among the three energy systems, probably has the greatest capacity to change with training. Repeated rowing efforts of 1-3 minutes above AT and using a work: recovery ratio 1:3 or 1:2 will permit sufficient time for large amounts of lactate to be cleared and resysnthesized.

In other words, if you row 3 minutes, then your recovery time between exercise bouts will double or triple the exercise time. This is not only an effective way to train the Lactic Acid System, but if exercise duration is extended, the cardiovascular transport system will also greatly benefit. Any work performed at or above AT will teach the athlete lactate tolerance and, as the exercise increases in intensity, so will the learning effect. The AT seems as receptive to change as the LAS.

It is not uncommon for an elite rower to improve AT from 70-75% of maximal heart rate during the off-season to 85-90% during the competitive period. Anaerobic Threshold training should include a work: recovery ratio of 1:1. Because training intensities above AT are almost totally dependent on glucose and glycogen for fuel, it is recommended that 36- 48 hours should separate any of these higher intensity workouts. Even a diet high in carbohydrate will be challenged to replenish muscle glycogen stores during these recovery times. I have often referred to AT as that point during high intensity exercise where an untrained person will stop exercising and where a trained athlete will begin to think about quitting; the latter being precisely the state of mind you want your opponent to be in with 250-500m to go in the race.

Part V: The Oxygen System

The Oxygen System, or aerobic metabolism, makes the most significant contribution of energy during a 2000m race and also for most training rows. Although more active biochemical changes seem to occur in the muscle cell as a result of aerobic training compared to only minimal changes attributed to anaerobic training, the actual increase in VO2 max is proportionally less than measurable responses of anaerobic factors due to specific training methods. Although it appears that VO2 max is primarily determined by hereditary factors, it can be significantly improved with training. However, its capacity for change is considerably less than the potential for change in the anaerobic response.

For many years, exercise scientists have suggested that VO2 max is the single most limiting factor in performing high intensity aerobic work that extends beyond 3 minutes. Although there is a strong relationship between VO2 max and a rower’s performance, our more recent research has shown that there is an even stronger relationship between a rower’s ability to work for 5-7 minutes at a higher percentage of their VO2 max and their performance.

The most revealing physiological response to predict rowing performance at the international level is the rower’s ability to maintain their metabolic rate at or above AT. Any aerobic athlete who can significantly elevate their AT can perform high intensity exercise more efficiently (aerobic metabolism means more ATP molecules) and the by-products of the O2 system, CO2 and H2O, are easy to deal with. This is not the case when anaerobic metabolism dominates.

Oxygen, or aerobic training, can be divided into either high intensity or low intensity workouts and both can use either continuous or intermittent training sessions. High intensity aerobic training seems more conducive to intermittent work, which should range from about 75-90% of maximal heart rate (see table of training intensities) with a work recovery ratio of either 1:0.5 or 1:0.25. In other words, if you row 10 minutes in this intensity range, your recovery period should range from 2.5 to 5 minutes. The high intensity form should not only represent the majority of your aerobic training but should also be the largest contributor to total training time.

Most low intensity aerobic training should be continuous and, if done intermittently, it should not be for any length of time less than 10 minutes. Rest or recovery periods for low intensity aerobic rowing should range between 30-60 seconds; the shorter the duration of exercise, the shorter the recovery period needed. Low intensity aerobic training is often referred to as “conversational” pace and thus you should be able to talk easily during an exercise of this intensity.

Although both forms of aerobic training permit a rower to reach and maintain an aerobic base, do not interpret the value of aerobic training in only quantitative terms. Every workout, even of a low intensity, must always stress quality, and as the physical condition of the rower improves, both exercise intensity and skill level need to be elevated. Many coaches and athletes are convinced that 60-120 minutes of continuous low intensity or steady-state rowing is an important part of developing and maintaining an adequate aerobic base. We have convincing data, including muscle biopsy histochemical and biochemincal indicators, which support that rowing continuously at a low steady state intensity for 60 minutes or longer for any calibre of rower, is not more effective in maintaining aerobic capacity than 30 minutes of rowing at the same work intensity.

Not only do these results apply to a single bout of rowing, but also to 5, 10, 15, and 20 week training responses after the aerobically-trained subjects had completed a total of 20, 40, 60 and 80 training sessions respectively. Furthermore, performing 2 intermittent 30 minute exercise bouts of relatively high aerobic work intensity (10-20 % more average power than for the low intensity work) with a 7-10 minute recovery period between the 30 minute work bouts is a much stronger aerobic training stimulus than lower intensity continuous rowing.

This higher work intensity for continuous rowing could not be tolerated by most subjects for more than 32-36 minutes and still maintain a steady-state. The increased energy expenditure of the intermittent high intensity work not only proved significantly more effective than either 30 or 60 minutes of rowing in the improvement of aerobic capacity, but it was also more neuromuscularly task specific.

Comparative videotape, coaching evaluations, and metabolic data confirmed those rowers performing intermittent high intensity training bouts rowed more efficiently at all exercise intensities than those rowers who trained for longer time periods and at lower intensities, especially as stroke rating and power output increased to beyond AT, including maximum power output.

This presentation has discussed training of all three basic energy systems, including AT training with supporting research data to validate my recommendations. Regardless of your present skill level or physical conditioning state or your competitive aspirations, optimal training of the energy systems requires a comprehensive training program. In future irow.com presentations, the importance of comprehensiveness will be emphasized by discussions dealing with such topics as resistance training, cross training, artificial and actual altitude training, restricted breathing training, high oxygen training, ionization training, electrical stimulation of muscle, and muscle and blood boosting using creatine, human growth hormone, erythropoietin (EPO), and oxygen “kickers” such as flurocarbons, oxygen breathing, and oxygenated water.


Saturday
Aug132011

The Anaerobic Aspects of Resistance Training 

By: Bruce W Craig PhD
Site Link: NSCA


 

Introduction

Resistance training has become the common term to describe exercise involving any form of resistance, be it free weights, machines, elastic bands, pulley systems, or body weight as used in some exercise equipment. The lifting of weights comes under this broad umbrella and can be separated into a variety of categories (11) but most weight exercises can be performed for a variety of sets and repetitions and resistances, with somewhat different outcomes. There are some basic differences between training for strength and hypertrophy (muscle size) compared to training for power (explosive strength) which is a major component of most sports. However, all forms of resistance training rely on anaerobic metabolism for their energy needs. The purpose of this brief review is to explain how anaerobic metabolism supplies that energy and how these forms of training differ in their usage.

Muscle Transition

Strength is based on the ability to produce force, and the amount generated is dependent on the motor unit (neuron and muscle fibers it innervates) recruitment pattern that is established. Newton’s second law of physics defines force as F = ma, with m representing mass and a standing for acceleration. Mass is represented by the workload or the amount of weight moved, and acceleration involves the speed at which the weight is moved. These two components of force set the neural recruitment pattern by determining the type and number of motor units to be used, and their rate of activation.

The neurons of motor units stimulate either type I or type II muscle fibers. Type I fibers (slow twitch) contain numerous mitochondria, require oxygen to function, produce low to moderate amounts of force, and are fatigue resistant. These characteristics make them ideal for supplying the bulk of the energy when not much force is required, but must be maintained for long periods of time, such as when standing. Type II fibers (fast twitch) on the other hand, have fewer mitochondria, are more anaerobic in nature, and produce more force than type I fibers. However, they do fatigue more rapidly than type I, and come in two varieties; IIa and IIx (formally termed IIb) (2,15). The IIa form of these fast twitch fibers have the ability to use oxygen to make Adenosine Tri-phosphate (ATP) but have a high dependency on anaerobic forms of metabolism, such as glycogen breakdown which produces lactic acid. Prolonged bouts of high intensity anaerobic training can therefore produce significant amounts of lactic acid (7) in type IIa muscle fibers. The accumulation of lactic acid within the type IIa muscle fibers causes the pH to drop, and leads to fiber fatigue (1). Type IIx fibers are almost purely anaerobic in nature and fatigue even quicker than IIa fibers but become the primary fiber of choice during maximal force production and when IIa fibers become fatigued (2,15). Several studies have shown that repeated bouts of resistance exercise can transform IIx fibers into IIa fibers (10, 13,16,). The transition of IIx fibers into IIa fibers is an important part of the adaptation that resistance training produces and is discussed in more detail in the subsequent sections.

Strength and Hypertrophy Adaptations

In training to optimize hypertrophy, sets are typically performed at 60-75% of the 1RM (8-12 repetitions), and have a shorter work to rest ratio (1-1.5 min). Optimizing strength involves training at higher loads (80-90% 1RM) with fewer reps (4 to 6) and a longer work:rest ratio (2-3 min) (14). Although not obvious by the set and rep combinations, there is a lot of overlap between the physiological adaptations to hypertrophy and strength training, such that one still increases strength somewhat with hypertrophy-focused training and one still increases size somewhat with strength-focused training. Te overall effect of these forms of training is that they push the muscles to the point of fatigue. Fatigue is defined as the in- ability to maintain force, and as indicated above can increase type IIa fiber numbers. The work of several investigators (10, 13,16) has shown that muscles of untrained individuals contain hybrid muscle fiber types in addition to the type I, type IIa, and type IIx fibers, the hybrids being muscle fibers that are going through a transition from type IIa to I (9) or from type IIx to IIa (10,13,16). The muscles of highly trained athletes, on the other hand, contain few hybrid fibers (2). Te increase in IIa fiber number induced by strength and hypertrophy training enhances the anaerobic capacity of muscles by forcing them to adapt to repeated bouts of exercise that depend on anaerobic metabolism (6,12).

Although there are no definitive studies that have measured the enzymatic alterations that resistance training induces, the work of MacDougall et al. (8) does indicate the type of change that can occur. The subjects in this investigation under- went 7 weeks of sprint training on a cycle ergometer. Training started with four 30 sec maximal exercise bouts (Wingate protocol) with 2-4 min recovery between them, and the subjects trained three days per week. By the end of the 7 weeks they completed ten 30 sec rides three times per week. They found that the subjects’ peak power, total work and VO2max was significantly increased by training, and attributed it to the significant increases in both aerobic (malate dehydrogenase, succinate dehydrogenase, and citrate synthase) and anaerobic (phosphofructokinase and hexokinase) enzyme activity. It might seem odd that the training improved both forms of metabolism until the accumulation of lactic acid and its ability to induce fatigue is taken into account. The primary effect of the muscle fiber transition is that IIx fibers, that are almost entirely anaerobic in nature, become IIa fibers that can use both aerobic and anaerobic metabolism. Therefore, the stress represented by repeated bouts of high intensity exercise converts the enzymatic composition of the IIx fibers to a IIa form of metabolism, and increases both oxidative and non-oxidative capability of the muscle. This enables the muscle to use a greater amount of glucose and/or glycogen with less build-up of lactic acid. This was demonstrated in a resistance training study conducted by Keeler (6).

Power Adaptations

Power forms of lifting are more explosive in nature than strength and hypertrophy training. Although the sets and repetitions and rest periods are similar to that of strength-focused training, the amount of weight lifted can be as low as only body weight, up to about 40% of the 1RM, except in the case of the Olympic lifts, which are performed at 70-80% 1RM. Te lifter is required to exert maximal power to get the weight moving, and the only way that can be done is by training the nervous system to recruit as many type IIa fibers as possible. However, before an individual can train explosively they have to build a strength base.

Acceleration enables the establishment of movement velocity (speed) but is directly related to the rate of force development (RFD) generated with the initiation of movement. In strength and hypertrophy the lifter concentrates on the movement patterns of concentric and eccentric phase of the lift and tries to maintain a steady rhythm. The lift can even be performed slowly to maximize the fatiguing aspects of the exercise (3). Explosive lifts, on the other hand, are dependent on the neural recruitment of large numbers of type IIa muscle fibers to get the weight moving as quickly as possible. Therefore, any improvement in the RFD is a very important aspect of training.

Hakkinen et al. (4) demonstrated that strength and hypertrophy training can enhance peak strength but it does not affect the RFD, whereas power training does significantly improve the RFD. Although the anaerobic breakdown of glycogen (7) is used to some degree during an explosive lift, the primary energy source is ATP and the regeneration of ATP via the breakdown of creatine phosphate (CP). It is what gives the lifter the ability to explode and is why the rest period between lifts is longer. The extra time is needed to re-establish the ATP and CP stores of the muscle fibers. To date no one has examined the ATP and CP turnover in power forms of lifting but these factors have been examined with sprint training. Harmer et al. (5) sprint trained athletes for 7 weeks using a protocol that was similar to that used by MacDougal et al. (8) and found that the rate of anaerobic ATP usage following training was approximately half of what it was before training, whereas CP turnover was the same. They did not address this issue in their discussion but the data implies that the biomechanical improvements (better neural recruitment) might be responsible for the decline in ATP usage.

Anaerobic metabolism is dependent on the percentage of type IIa muscle fibers within the body. Tat percentage can be altered with training. Untrained individuals have a higher percentage of undifferentiated fibers (hybrids) than highly trained athletes. Resistance training is an effective way to enhance the muscle profile and increases the number of fast twitch fibers (type IIa) it contains. Although type I muscle fibers can increase in diameter with training it is the type IIa fibers that undergo the greatest hypertrophy with resistance training and are the basis for the increase in strength that is achieved from this form of training (2,15). The added benefit is that the anaerobic capacity also increases due to an enzymatic conversion that occurs with muscle fiber transition. Although power training depends more on ATP and CP than glycogen for energy needs it still requires a high percentage of type IIa muscle fibers. Once this fiber type is established with resistance training, power forms of training will enable an athlete to maximize the neural recruitment of type IIa fibers

References

Craig BW: Does muscle pH affect performance? Strength and Conditioning Journal 26:24 – 25, 2004

Fleck SJ, Kraemer WJ: Designing Resistance Training Programs. Champaign, IL, Human Kinetics, 2004

Greer BK: Superslow Training. NSCA Hot Topics Series, 2006

Hakkinen K, Komi PV, Alen M: Effect of explosive-type strength training on isometric force- and relaxation-time, electromyographic and muscle fiber characteristics on leg extensor muscles. Acta Physiologica Scanainavica 125:587 – 600, 1985

Harmer AR, McKenna MJ, Sutton JR, Snow RJ, Ruell PA, Booth J, Tompson MW, Mackay NA, Stathis CG,

Crameri RM, Carey MF, Eager DM: Skeletal muscle metabolic and ionic adaptations during intense exercise following sprint training in humans. Journal of Applied Physiology 89:1793 – 1803, 2000

Keeler LK, Finkelstein LH, Miller W, Fernhall B: Early-phase adaptations of traditional-speed vs. superslow resistance training on strength and aero- bic capacity in sedentary individuals. Journal of Strength and Conditioning Research 15:301 – 314, 2001

Kraemer WJ, Noble BJ, Culver BW, Clark MJ: Physiologic responses to heavy-resistance exercise with short rest periods. International Journal of Sports Medicine 8:247 – 252, 1987

MacDougal JD, Hicks AL, MacDonald JR, McKelvie RS, Green HJ, Smith KM: Muscle performance and enzymatic adaptations to sprint interval training. Journal of Applied Physiology 84:2138 – 2142, 1998

Saltin B, Gollnick PD: Skeletal muscle adaptability: Significance for metabolism and preformance. In Handbook of Physiology

Peachy L, Adrian R, Gerzer SR, Eds. Bethesda, MD, American Physiological Society, 1983, p. 555 – 631

Staron B, Malicky ES, Leonardi MJ, Falkel JE, Hagerman FC, Dudley GA: Muscle hypertrophy and fast fiber type conversions in heavy resistance- trained women. European Journal of Applied Physiology and Occupational Physiology. 60:71 – 79, 1990

Stone MH, Pierce KC, Sands WA, Stone ME: Weightlifting: A brief overview. Strength and Conditioning Journal 28:50 – 66, 2006

Tavino L, Bowers CJ, Archer CB: Effects of basketball on aerobic, anaerobic capacity, and body composition of male college players. Journal of Strength and Conditioning Research 9:75 – 77, 1995

Trappe SW, Williamson D, Godard MP, Porter D, Rowden G, Costill DL: Effect of resistance training on single muscle fiber contractile function in older men. Journal of Applied Physiology 89:143 – 152, 2000

Triplett NT: Specificity for Sport. NSCA Hot Topics Series, 2006

Wilmore JH, Costill DL: Physiology of Sport and Exercise. Champaign, IL, Human Kinetics, 2004

Williamson DL, Godard MP, Porter D, Costill DL, Trappe SW: Maintenance of whole muscle strength and size following resistance training in older men. Journal of Gerontology: Biological Sciences. 27A:B138 – B143, 2002


Saturday
Jul302011

How To Determine Lactate / Anaerobic Threshold

By: Sports Advisor.
Site link: Sports Advisor.

There are several methods used to determine an athletes lactate or anaerobic threshold. While the most accurate and reliable is through the direct testing of blood samples during a graded exercise test, this is often inaccessible to most performers.

There are several field tests that can also be used to estimate lactate threshold. They vary in their reliability but some offer an acceptable alternative for most amateur athletes.

Several terms such as onset of blood lactate accumulation and maximal lactate steady state are used interchangeably with anaerobic threshold. Technically, they do not describe precisely the same thing. In fact, although lactate threshold and anaerobic threshold occur together under most conditions, strictly speaking even these two terms are not the same (1). For this article however, lactate threshold and anaerobic threshold will be used interchangeably. See the lactate threshold article for more details on this topic.

It is also worth bearing in mind that blood lactate and lactic acid are not the same substance. Blood lactate production is actually thought to be beneficial to endurance performance and may delay fatigue. Nevertheless, its accumulation still remains a good marker for the onset of fatigue. 

Laboratory Testing of Anaerobic Threshold

The most accurate way to determine lactate threshold is via a graded exercise test in a laboratory setting (2). During the test the velocity or resistance on a treadmill, cycle ergometer or rowing ergometer is increased at regular intervals (i.e. every 1min, 3min or 4min) and blood samples are taken at each increment. Very often VO2 max, maximum heart rate and other physiological kinetics are measured during the same test (3).

Blood lactate is then plotted against each workload interval to give a lactate performance curve. Heart rate is also usually recorded at each interval often with a more accurate electrocardiogram as opposed to a standard heart rate monitor.

Once the lactate curve has been plotted, the anaerobic threshold can be determined. A sudden or sharp rise in the curve above base level is said to indicate the anaerobic threshold. However, from a practical perspective this sudden rise or inflection is often difficult to pinpoint.

Assuming the inflection is clear (as in the graph above), the relative speed or workload at which it occurs can be determined. In this example, the athletes anaerobic threshold occurs at about 12km/h. This means, in theory they can maintain a pace at or just below 2km/h for a prolonged period, indefinitely. Of course, this is purely hypothetical as there are many other factors involved in fatigue not least the amount of carbohydrate stores an athlete has in reserve (1). A crossover to fat metabolism will significantly reduce the athletes race pace (2).

By recording heart rate data alongside workload and blood lactate levels, an athlete can use a heart rate monitor to plan and complete training sessions. Although monitoring heart rate is never completely reliable and varies greatly between and within individuals (1,2,3) combining it with lactate measurements is probably more reliable than using the Conconi test (see below) for example.

Confirmatory Test

When anaerobic threshold is read from the lactate curve, an additional test can be used to verify its accuracy. Using the example above, the athletes threshold is thought to occur at about 12km/h on the treadmill. The confirmatory test involves running for 15 minutes at a pace just below threshold, 15 minutes at threshold and 15 minutes at a pace just above threshold. See the curves below of three athletes whose thresholds have all been determined to occur at approximately 12kmh.

Notice that for Athlete 1, blood lactate remains steady at their estimated anaerobic threshold (12km/h) and lactate begins to accumulate when the pace is increased to 13km/h in the final 15 minutes. For athlete 1, this is confirmation that their anaerobic threshold pace is reasonably accurate.

For Athlete 2, lactate begins to accumulate during the middle 15minute segment (their estimated threshold) and continues to do so during the final 15 minutes. For this athlete, anaerobic threshold occurs at a slightly slower pace than was determined originally.

Finally, Athlete 3s lactate curve does not rise significantly even during the final 15 minutes segment. Anaerobic threshold for them occurs at a slightly higher pace then was originally determined.

Assuming, you dont have access to facilities that directly monitor your or your athletes lactate response, are there other acceptable alternatives?

Portable Lactate Analyzer

Portable lactate analysers are becoming more popular amongst coaches and athletes at all levels. A good portable analyzer should have the same validity and reliability as laboratory testing equipment. The Accutrend Lactate Analyzer for example, has been tested using guidelines of the European Committee for Clinical Laboratory Standards and is cleared for sports medicine use by the Federal Drug Administration in the United States.

Needless to say a portable analyser is only one half of the equation. A suitable and sport-specific exercise test is still required and selecting the most appropriate protocol takes knowledge and experience. Any physiological test is only as reliable as the testers ability to follow a set protocol. Even when a suitable assessment has been chosen, numerous variables must be kept constant for the test to remain accurate and reliable.   

Conconi Test

In 1982 Conconi et a (4) stated that the anaerobic threshold correlated to a deflection point in the heart rate. Essentially, heart rate and exercise intensity is linear i.e. as exercise intensity increases so will heart rate. However, Conconi et a found that in all their tested subjects, including those in a follow up test (5), heart rate reached a plateau at near maximal exercise intensities.

Although this is a relatively simple field test that would be useful for coaches and athletes at all levels, its accuracy has been contested by subsequent researchers (6,7,8). Studies have found that the deflection point or plateau in heart rate only occurs in a certain number of individuals and that when it does, it significantly overestimates directly measured lactate threshold. Conconi and co-workers (9) themselves acknowledge this controversy and cite studies that both support and contradict their original findings. 

10km Run, 30Km Cycle, 30 Min Time Trial

More experienced athletes often run a 10km race or cycle 30km race at or close to anaerobic threshold. By simulating a race in training and recording heart rate, the anaerobic threshold may be determined. Alternatively, exercising for 30 minutes at the fastest sustainable pace can be used. The key is to sustain a steady pace which is why this test is more suited to experienced athletes who can gauge how fast to set off. A heart rate monitor with split time facility is required to record heart rate at each 1-minute interval. Take the average heart rate over the final 20 minutes as the heart rate corresponding to anaerobic threshold.  

Heart Rate Percentage

A very simply method for estimating the anaerobic threshold is to assume anaerobic threshold occurs at 85-90% maximum heart rate (220-age). As mentioned earlier, heart rate varies greatly between individuals and even within the same individual so this is not a reliable test.

The Lactate Threshold Debate

Some researchers have questioned the validity of determining the lactate or anaerobic threshold even in laboratory settings (10,11). Yet more researchers question whether a definite point or threshold exists at all (10,12,13,14). Instead they suggest blood lactate accumulation is continuous in nature and no specific point can be determined.

Rather than get bogged down in the debate it is sensible to remember that regardless of the underlying mechanisms, the physiological changes that accompany lactate accumulation have important implications for endurance athletes. Any delay in the blood lactate accumulation that can be achieved through training is beneficial to performance.

References

1) Wilmore JH and Costill DL. (2005) Physiology of Sport and Exercise: 3rd Edition. Champaign, IL: Human Kinetics

2) McArdle WD, Katch FI and Katch VL. (2000) Essentials of Exercise Physiology: 2nd Edition Philadelphia, PA: Lippincott Williams & Wilkins

3) Maud PJ and Foster C (eds.). (1995) Physiological Assessment Of Human Fitness. Champaign, IL: Human Kinetics

4) Conconi, F., M. Ferrrari, P. G. Ziglio, P. Droghetti, and L. Codeca. Determination of the anaerobic threshold by a noninvasive field test in runners. J. Appl. Physiol. 1982, 52: 862-873

5) Ballarin, E., C. Borsetto, M. Cellini, M. Patracchini, P. Vitiello, P. G. Ziglio, and F. Conconi. Adaptation of the "Conconi test" to children and adolescents. Int. J. Sports Med. 1989, 10: 334-338

6) Parker, D., R. A. Robergs, R. Quintana, C. C. Frankel, and G. Dallam. Heart rate threshold is not a valid estimation of the lactate threshold. Med. Sci. Sports Exerc. 1997, 29: S235

7) Tokmakidis, S. P., and L. A. Leger. Comparison of mathematically determined blood lactate and heart rate "threshold" points and relationship to performance. Eur. J. Appl. Physiol. 64: 309-317

8) Vachon JA, Bassett Jr DR and Clarke S. Validity of the heart rate deflection point as a predictor of lactate threshold during running. J Appl Physiol. 1999, 87: 452-459

9) Conconi, F., G. Grazze, I. Casoni, C. Guglielmini, C. Borsetto, E. Ballarin, G. Mazzoni, M. Patracchini, and F. Manfredini. The Conconi test: methodology after 12 years of application. Int. J. Sports Med. 1996, 17: 509-519

10) Yeh MP, Gardner RM, Adams TD, Yanowitz FG, Crapo RO. "Anaerobic threshold": problems of determination and validation. J Appl Physiol. 1983, Oct;55(4):1178-86

11) Gladden LB, Yates JW, Stremel RW, Stamford BA. Gas exchange and lactate anaerobic thresholds: inter- and intraevaluator agreement. J Appl Physiol. 1985 Jun;58(6):2082-9

12) Hughson RL, Weisiger KH, Swanson GD. Blood lactate concentration increases as a continuous function in progressive exercise. J Appl Physiol. 1987 May;62(5):1975-81

13) Campbell ME, Hughson RL, Green HJ. Continuous increase in blood lactate concentration during different ramp exercise protocols. J Appl Physiol. 1989 Mar;66(3):1104-7

14) Dennis SC, Noakes TD, Bosch AN. Ventilation and blood lactate increase exponentially during incremental exercise. J Sports Sci. 1993 Oct;11(5):371-5; discussion 377-8