Entries in Aerobic Capacity (4)

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.


Thursday
Aug112011

Training for intense exercise performance: high-intensity or high-volume training?

By: Paul B. Laursen
From: Team Danmark
Article Link: High-intensity and high volume training


Abstract

Performance in intense exercise events, such as Olympic rowing, kayak, track running and track cycling events, involves a mix of energy system contributions from aerobic and anaerobic sources. Aerobic energy supply however dominates the total energy requirements of these events after ~75 s of near maximal effort. As the aerobic energy system has the greatest potential for improvement with training, and intense exercise events generally persist for longer than 75 s, training methods for these events are generally aimed at increasing aerobic metabolic capacity. A short-term period (2-4 wk) of high-intensity interval training (HIT; consisting of repeated exercise bouts ranging in intensity from 80-175% of peak power) can elicit increases in intense exercise performance of 2-4% in well trained athletes. While the influence of high volume training (HVT) is less discussed, its importance should not be downplayed, as it may develop the aerobic base needed to support recovery and adaptation from HIT by promoting autonomic balance and athlete health. Indeed, when HIT is performed without a background of HVT, performance can be maintained, but is generally not improved. While the aerobic metabolic adaptations that occur with HVT and HIT are similar, the molecular events that signal for these adaptations may be different. The high levels of intramuscular calcium associated with HVT may signal for metabolic adaptations that improve muscle efficiency through the calcium-calmodulin pathway, while the brief low energy state created with HIT may elicit its effects through the adenosine monophosphate kinase pathway. These distinct molecular signaling pathways, which have similar downstream targets (i.e., mitochondrial biogenesis), may help to explain the potent effect that combined HVT and HIT has on aerobic energy system upregulation and intense exercise performance.

Introduction

Both high-intensity (short duration) training and low intensity (long duration) high volume training are important components of training programs for athletes who compete successfully in intense exercise events. In the context of this review, an intense exercise event is considered to be one lasting between 1 to 8 min, where there is a mix of adenosine triphosphate (ATP)-derived energy from both aerobic and anaerobic energy systems. Examples of such intense exercise events include individual sports such as Olympic rowing, kayak and canoe events, running events up to 3000 m, and track cycling events.

Exercise training, in a variety of forms, is known to improve the energy status of working muscle, subsequently resulting in the ability to maintain higher muscle force outputs for longer periods of time. While both high volume and high-intensity training are important components of an athlete’s training program, it is still unclear how to best manipulate these components in order to achieve optimal intense exercise performance in well trained athletes. While a short-term period of high-intensity training is known to improve performance in these athletes (Laursen & Jenkins 2002), it is also clear that high training volumes are of equal importance (Fiskerstrand & Seiler 2004). More recent work by exercise scientists is revealing how the combination of these distinctly different forms of training may work to optimize development of the aerobic muscle phenotype and enhance intense exercise performance.

The purpose of this discourse is to i) review the energy system contribution to intense exercise performance, ii) examine the effect of high-intensity training and high volume training on performance and physiological factors, iii) assess some of the molecular events that have been implicated in signaling for these important metabolic adaptations and iv) make recommendations, based on this information, for the structuring of training programs to improve intense exercise performance. 

Energy system contribution to intense exercise performance – what is it we are trying to enhance?

Intense exercise events involve a near maximal energy supply for a sustained period of time. These near-maximal efforts require a mix of anaerobic and aerobic energy provision. To illustrate this, Duffield et al. (2004; 2005a; 2005b) examined the aerobic and anaerobic energy system contributions to 100, 200, 400, 800, 1500 and 3000 m track running in well trained runners. The data from the male runners in these studies are plotted in Figure 1, revealing that the energy contribution to an intense exercise event arises from a mix of aerobic and anaerobic sources. The crossover point, where aerobic and anaerobic energy contributes equally, occurs approximately at 600 m of near maximal running. This compares well with an earlier crossover estimate made by Gastin (2001) of about 75 s of near-maximal exercise. Thus, for an intense exercise event that lasts beyond 75 s, total energy output is mostly aerobically driven. This is a convenient situation for the exercise conditioner, because the aerobic energy system appears to be a more malleable system to adjust. Indeed, both high-intensity and high-volume training can elicit improvements in aerobic power and capacity.

Effect of training on physiological variables and intense exercise performance

The purpose of exercise training is to alter physiological systems in such a way that physical work capacity is enhanced through improved homeostasis preservation during subsequent exercise sessions. Manipulation of the intensity and duration of work and rest intervals changes the relative demands on particular metabolic pathways within muscle cells, as well as oxygen delivery to muscle. In response, changes occur in both central and peripheral metabolic systems, including improved cardiovascular dynamics (Buchheit et al. 2009), neural recruitment patterns (Enoka & Duchateau 2008), muscle bioenergetics (Hawley 2002), as well as enhanced morphological (Zierath & Hawley 2004), metabolic-substrate (Hawley 2002) and skeletal muscle acid-base status (Hawley & Stepto 2001). The rate at which these adaptations occur is variable (Vollaard et al. 2009), but appears to depend on the volume, intensity and frequency of the training. Importantly, development of the physiological capacities witnessed in elite athletes do not occur quickly, and may take many years of high training loads before peak levels are reached.

Training can be structured in an infinite number of ways, but in general, coaches tend to prescribe periods of prolonged submaximal or shorter high-intensity exercise sessions. Submaximal endurance training performed for long durations, involves predominantly slow twitch motor unit recruitment, while higher intensity training (usually completed as high-intensity interval training) will recruit additional fast twitch motor units for relatively short durations. Both forms of training are important for enhancing the aforementioned physiological systems and intense exercise performance, but the degree and rate at which these variables change in the short term appears to be affected more acutely by high-intensity training (Londeree 1997). 

Performance and physiological effects of additional training intensity

The marked influence of high-intensity training on performance and physiological factors is well known (Laursen & Jenkins 2002), but an athlete’s ability to perform this type of training may be limited. One successful method of performing higher volumes of high-intensity training is termed high-intensity interval training. High-intensity interval training is defined as repeated bouts of high-intensity exercise (i.e., from lactate threshold to ‘all-out’ supramaximal exercise intensities), interspersed with recovery periods of low intensity exercise or complete rest.

In already well trained athletes, the effect of supplementing high-intensity training on top of an already high training volume appears to be extremely effective. In well trained cyclists, high-intensity interval training, completed at a variety of intensities (i.e., 80 – 150% VO2max power output) for two to four weeks, has been shown to have a significant influence (i.e., 2-4%) on measures of intense exercise performance (i.e., time-to-fatigue at 150% of peak power output), peak power output, and 40-km time trial performance (Lindsay et al. 1996; Stepto et al. 1998; Westgarth-Taylor et al. 1997; Weston et al. 1997). In well trained middle distance runners, Smith and colleagues (1999; 2003) found improvements in 3000 m running performance when runners performed high-intensity interval training (8 x ~2-3 min at VO2max running speed, 2:1 work to rest ratio) twice a week for four weeks. In a retrospective study performed on elite swimmers Mujika et al. (1995) found that mean training intensity over a season was the key factor explaining performance improvements (r = 0.69, p < 0.01), but not training volume or frequency. Clearly, a short-term period of high-intensity interval training supplemented into the already high training volumes of well trained athletes can elicit improvements in both intense and prolonged exercise performance (Laursen & Jenkins 2002).

While the potent influence that a short-term dose of high-intensity interval training has on intense and prolonged endurance performance is well known, the mechanisms responsible for these performance changes with well trained individuals are not clear. For example, Weston et al. (1997) had six highly trained cyclists perform six high-intensity interval training sessions (8 x 5 min at 80% peak power output, 60s recovery) over three weeks, and showed significant improvements in intense exercise performance (time to fatigue at 150% peak power output) and 40 km time trial performance, without changes in skeletal muscle glycolytic or oxidative enzyme activities.   Thus, despite the likely high rates of carbohydrate oxidation (340 µmol.kg-1.min-1) required by these efforts (Stepto et al. 2001), this acute perturbation in energy status of working muscle did not appear to increase metabolic enzyme function in the skeletal muscle of these six cyclists (Weston et al. 1997), as would be predicted based on findings made in less trained subjects (Gibala & McGee 2008). Instead, an increase in skeletal muscle buffering capacity was reported (Weston et al. 1997). Other physiological factors that have been shown to increase in parallel with improvements in performance following the addition of high-intensity interval training to the already high training volume of the well trained athlete include improvements in the ventilatory threshold (Acevedo & Goldfarb 1989; Hoogeveen 2000), an increased ability to engage a greater volume of muscle mass (Creer et al. 2004; Lucia et al. 2000) and an increased ability to oxidize fat relative to carbohydrate (Westgarth-Taylor et al. 1997; Yeo et al. 2008).

In a recent study, Iaia et al. (2008; 2009) asked runners who were training 45km/wk to lower their training volume to only 15 km/wk for 4 weeks, and instead perform sprint training (8-12 x 30s sprints; 3-5 times/wk). After this distinct change in training, runners in the sprint training groups had maintained their 10 km run performance, VO2max, skeletal muscle oxidative enzyme activities and capillarisation compared with the 45km/wk control group (Iaia et al. 2009). However, 30-s sprint (+7%), Yo-Yo intermittent recovery test (+19%) and supramaximal running (+19-27%) performances had increased in the sprint training group (Iaia et al. 2008). This study indicates that low volume high-intensity interval training can maintain an athlete’s endurance performance and muscle oxidative potential (Iaia et al. 2009), and additionally increase intense exercise performance (Iaia et al. 2008).

High-intensity interval training has also been shown to be effective at enhancing various aspects of team sport performance. For example, Helgerud et al. (2001) showed that 8 weeks of high-intensity interval training (4 x 4 min @ 95% HRmax, 3 min recovery jog, twice per week) enhanced distance covered during a match (20%), number of sprints (100%), number of ball involvements (24%) and average work intensity during a match. More recently, Bravo et al. (2008) showed that 7 weeks of repeated sprint run training (3 x 6 maximal shuttle sprints of 40 m) was more effective at enhancing Yo-Yo intermittent recovery test performance and repeated sprint ability compared with traditional interval training (4 x 4 min running at 90-95% HRmax).

Finally, when high-intensity training can be woven into training programs using ball-specific drills or small-sided games, markers of intense exercise performance can also be enhanced, with the added benefit of simultaneously receiving skill-based training (Impellizzeri et al., 2006; Buchheit et al., 2009).

In summary, it is clear that when a period of high-intensity interval training is supplemented into the already high training volumes of well trained endurance athletes, further enhancements in both intense and prolonged endurance performance are possible. As well, lower volume high-intensity interval training can maintain endurance performance ability in already well trained endurance athletes. High-intensity interval training inserted into the training programs of team sport athletes is not only effective at enhancing markers of endurance capacity, but can also improve various aspects of game-specific performance. Nevertheless, while high-intensity training can have the aforementioned profound effects on various aspects of intense exercise performance, the importance of a high training volume background should not be overlooked.

Performance and physiological effects of additional training volume

As concluded by Costill and colleagues (1991), “it is difficult to understand how training at speeds that are markedly slower than competitive pace for 3-4 h.d-1 will prepare (an athlete) for the supramaximal efforts of competition”. Nevertheless, it is well known that athletes involved with intense exercise events perform a number of long duration, low intensity training sessions per week, resulting in high weekly training volumes. Indeed, it has been estimated that well-trained (including world-elite) athletes perform ~75% of their training at intensities below the lactate or ventilatory threshold, despite competing at much higher intensities (Seiler and Kjerland, 2006). This type of training likely contributes to the high energy status of their skeletal muscle (Yeo et al. 2008), their ability to sustain high muscular power outputs for long durations, and their ability to recover from high-intensity exercise. Relative to the number of studies showing enhancements in intense exercise performance with high-intensity interval training, there are relatively few studies documenting improvements in performance with increases in training volume. This may be due to the fact that the time-course for performance improvement with high volume training does not occur as rapidly compared with high intensity training, making investigation into its influence difficult for researchers. In one study that managed to achieve this, Costill and co-workers (1991) divided collegiate swimmers into groups that trained either once or twice a day for six weeks. As a result, one group performed twice the volume of training than the other (4,950 m.d-1 vs. 9,435 m.d-1) at similar high training intensities (95 vs. 93.5% VO2max). Despite higher levels of citrate synthase activity from the deltoid muscle shown in the group that doubled their training volume, performance times following a taper over distances ranging from 43.2 to 2743 m were not different between the groups. While this study demonstrates that a relatively acute period of high volume training (with similar high training intensities) does not appear to enhance performance, the subtle effects of low intensity high training volumes over time should be realized.

The importance of low intensity long duration training sessions has been shown in at least two studies. In one longitudinal study conducted over a six-month period, Esteve-Lanao et al. (2005) compared the influence of different amounts of intensity and volume training on running performance in eight sub-elite endurance runners (VO2max = 70.0±7.3 mL.kg.min-1).

The authors found strong relationships between time spent training at intensities below the ventilatory threshold and both 4 km (r=-0.79; P=0.06) and 10 km (r=-0.97; P=0.008) run performance (Esteve-Lanao et al. 2005). In another study, Fiskerstrand and Seiler (2004) retrospectively investigated changes in training volume, intensity and performance in 21 international medal-winning Norwegian rowers over the years from 1970 to 2001. From the 1970s to the 1990s, VO2max increased by 12% (5.8 to 6.5 L.min-1) while 6-min rowing ergometer performance increased by 10%. In parallel with these performance changes was an increase in low intensity training (i.e., blood lactate <2 mM; 30 h.wk-1 to 50 h.wk-1), or high training volume, coupled with reductions in race pace and supra-maximal intensity training (blood lactate 8-14 mM; 23 h.wk-1 to 7 h.wk-1). As a result, training volume increased by 20% over this period of time (924 to 1128 h.yr-1), as did intense exercise performance results (Fiskerstrand & Seiler 2004).

While the immediate effect of high training volumes on intense exercise performance is difficult to assess, it would appear that the insertion of these low-intensity training sessions has a positive impact on performance, despite being performed at an intensity that is markedly less than that which is specifically performed at during intense exercise competition. These relatively low intensity, high training volumes may be a crucial part of competitive training programs and may provide a platform for the specific adaptations that occur in response to the high-intensity or specific workouts. 

The important interplay between high-intensity and high-volume training

The review of studies that manipulate training intensity and volume over a short-term period reveals that successful training programs may benefit from both forms of training at particular periods within an athlete’s training program. When training does not have an appropriate blend of both high-intensity and high volume training inserted into the program, performance ability tends to stagnate. For example, Iaia et al. (2008; 2009) examined the influence of marked changes in intensity and volume training on performance and metabolic enzyme activity in endurance-trained runners. In this study, runners training 45km/wk lowered their training volume to only 15 km/wk for 4 weeks, but instead performed sprint interval training (8-12 x 30s sprints; 3-5 times/week). While markers of sprint performance were improved, 10 km run performance was only maintained, and not enhanced (Iaia et al. 2008; 2009). In a study on competitive swimmers, Faude et al. (2008) used a randomised cross-over design where swimmers performed two different 4-wk training periods, each followed by an identical taper week. One training period was characterized by a high training volume, while the other involved high intensity training; neither program involved aspects of both. The authors found no difference between the training periods for 100 m or 400 m swim performance times, or individual anaerobic thresholds (Faude et al. 2008). Clearly, a mix of both high-intensity and high volume training is important, but predominance of one form of training or the other does not seems to be as beneficial. In a study demonstrating the importance of having equal amounts of distinctly different training, Esteve-Lanao et al. (2007) divided 12 sub-elite runners into two separate groups that performed equal amounts of high-intensity training (~8.4% of training above respiratory compensation point). The difference between the groups in terms of their training however was the amount of low vs. moderate-intensity training they performed. In one group, more low-intensity training (below the ventilatory threshold; 81% vs. 12%) was performed. In the other group, more moderate-intensity training (above ventilatory threshold but below respiratory compensation point; 67 vs. 25%) was performed. While intense exercise performance was not assessed, it is interesting to note that the magnitude of the improvement in 10.4 km running performance 5 months following the intervention was significantly greater (p = 0.03) in the group that performed more low-intensity training (-157 ±13 s vs. -122 ±7 s). Admittedly, the 10.4 km test used to assess running performance falls outside of the intense exercise spectrum, but does suggest that the aerobic power and capacity of these runners was enhanced by this training scheme; a capacity identified previously in this article as critical to intense exercise performance success beyond ~75 s of all-out near maximal activity.

The synthesis of these studies reveals the importance of combining periods of both high and low intensity training into the training programs of the intense exercise athlete. Seiler and Kjerland (2006) refer to this training distribution as a polarized model, where approximately 75% of sessions are performed below the first ventilatory threshold, with 15% above the second ventilatory threshold or respiratory compensation point, and <10% performed between the first and second ventilatory thresholds. For the exercise scientist, these observations beg the question: why might the mixing of distinct high- and low-intensity training sessions be so effective at increasing the energy status of working muscle and subsequent exercise performance? 

How does it happen?  Beginning to understand molecular signaling

While the picture is far from complete, scientists have begun to make impressive inroads towards understanding how skeletal muscle adapts to varying exercise stimuli, and for an excellent review on the topic, the reader may refer to the work of Coffey and Hawley (2007). As assessed by these authors (Coffey & Hawley 2007), there appear to be at least four primary signals (along with a number of secondary messengers, redundancy and cross-talk) that can lead to an increase in mitochondrial mass and glucose transport capacity in skeletal muscle following several forms of exercise training. These include i) mechanical stretch or muscle tension, ii) an increase in reactive oxygen species that occurs when oxygen is processed through the respiratory pathways, iii) the increase in muscle calcium concentration as required for excitation-contraction coupling, and iv) the altered energy status (i.e., lower ATP concentrations) in muscle. These mechanisms and pathways are complex, with many beyond the scope of this review. For the purpose of this discourse however, the focus will be on the last two of these primary signals, which have received increased attention in recent studies.

The first of these mentioned molecular signals is the prolonged rise in intramuscular calcium, such as that which occurs during prolonged endurance exercise or high exercise training volumes. These high calcium concentrations activate a mitochondrial biogenesis messenger called the calcium–calmodulin kinases (Figure 2). Second, the altered energy status in muscle associated with reductions in ATP concentrations, such as that present during high-intensity exercise, elicits a concomitant rise in adenosine monophosphate (AMP), which activates the AMP-activated protein kinase (AMPK). With these two secondary phenotypic adaptation signals identified, it becomes apparent how different types of endurance training modes might elicit similar adaptive responses (Burgomaster et al. 2008). In support of these distinct pathways, Gibala et al. (2009) showed significant increases in AMPK immediately following four repeated 30-s ‘all-out’ sprints. This was associated 3 hours later with a two-fold increase in peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) mRNA, a transcriptional coactivator that has been described by some as the ‘master switch’ for mitochondrial biogenesis (Adhihetty et al. 2003) (Figure 2). Of note, however, is that this occurred without an increase in the calcium–calmodulin kinases (Gibala et al. 2009), which are known to be stimulated during prolonged repeated contractions (Rose et al. 2007).

With these results in mind, it becomes clear what has been known by coaches for decades; that is, with respect to prescribing training that improves performance, “there’s more than one way to skin a cat”. The high mitochondrial oxidative capacity, improved fat oxidation and glucose transport in the skeletal muscle of endurance athletes may be achieved through either high volumes of endurance training, high intensities of endurance training, or various combinations of both. Higher volumes of exercise training are likely to signal for these adaptations through the calcium–calmodulin kinases (Rose et al. 2007), while higher intensities of endurance training, which lowers ATP concentrations and raises AMP levels, appear more likely to signal for mitochondrial biogenesis through the AMP-activated protein kinase pathway (Gibala et al. 2009). As shown in Figure 2, these different signaling molecules have similar downstream targets (Baar 2006). The result is an increased capacity to generate ATP aerobically. Thus, at the molecular level it may be the blend of signals induced from combined high volume and high-intensity training that elicits either a stronger or more frequent promotion of the aerobic muscle phenotype through PGC-1α mRNA transcription (Figure 2). As well, the lower intensity higher volume training sessions are likely to promote autonomic balance by facilitating recovery and muscle remodeling based on the molecular signals received from the high-intensity training sessions.

How do we optimally structure training programs for high performing endurance athletes?

The synthesis of this information reveals a pattern highlighting the importance of applying periods of both high-intensity and high volume training at the appropriate time in a training program, in order to elicit optimal intense exercise performance. Experts in training program design refer to this art as periodisation (Issurin 2008). While the importance of the high-intensity interval training stimulus appears to be critical (Londeree 1997), the submaximal or prolonged training durations (volume of repeated muscular contractions) cannot be downplayed (Fiskerstrand & Seiler 2004). These high volume training periods likely form the aerobic base needed for the rapid recovery between high-intensity training bouts and sessions. Over time, the progressive result is likely to be an improved efficiency of skeletal muscle and a development of the fatigue resistance aerobic muscle phenotype. Indeed, development of the successful intense exercise athlete tends to require a number of years exposure to high training volumes and intensities (Schumacher et al. 2006). The low intensity high training volumes also likely promote the recovery and autonomic balance needed for the facilitation of the mitochondrial protein synthesis signaled for through the high-intensity interval training sessions. The art of successful intense exercise coaching, therefore, appears to involve the manipulation of training sessions that combine long duration low-intensity periods with phases of very high-intensity work, appropriate recovery, and tapering (Mujika et al. 2000; Issurin 2008; Pyne et al. 2009). These same principles are likely to apply for team sport athletes, although other forms of training should likely be incorporated, such as plyometric training (i.e., drop jumps and countermovement jumps), which has recently been shown to improve agility time in semiprofessional football players (Thomas et al. 2009).

The paper will finish with two practical examples that demonstrate the effectiveness of this model. The first example is New Zealand’s Olympic 800 m running legend, Sir Peter Snell. Snell was a protégé of the late New Zealand athletics coach Arthur Lydiard, who was renowned for prescribing very high training volumes to his athletes who performed intense track events. Throughout his years of training, Snell was prescribed training volumes that would replicate those performed by most marathon runners (~160 km per week, interspersed with weekly high-intensity track workouts; P Snell, personal communication). The result was an 800 m world record in 1962 (1:44.3), and winning double Gold in the 800 m and 1500 m events at the 1964 Tokyo Olympic Summer Games.

In another report of a high training volume plan that elicited a winning intense exercise performance was that of the German 4000-m team pursuit cycling world record achieved at the Sydney 2000 Olympic Games (Schumacher & Mueller 2002). In this paper, Schumacher and Mueller (2002) provide a detailed account of the training performed by the cyclists over the 7 month lead-up to the critical event. In general, training involved extremely high training volumes (29,000 – 35,000 km/yr) that included long periods of low-intensity road training (~50% VO2max) interspersed with stage racing (grand tour) events. While the road racing component of the cyclists’ training program would have entailed numerous periods of both high volume and high intensity stimuli, it wasn’t until the final 8 days prior to the Sydney Olympics that a specific high intensity training taper period on the track was prescribed. Nevertheless, this training design yielded outstanding results, and the model has since been replicated by both the Australian and British cycling teams to break this record repeatedly over the last two Olympic Games (M. Quod, Cycling Australia, Australian Institute of Sport, Personal Communication).

Summary

Our understanding of how best to manipulate the training programs of athletes competing in intense exercise events so that performance is optimised is far from complete. It would appear that a polarised approach to training is optimal, where periods of both high-intensity and low intensity but high volume training are performed. The supplementation of high-intensity training to the high volume program of the already highly trained athlete can elicit further enhancements in endurance performance, which appears to be largely due to an improved ability of the engaged skeletal muscle to generate ATP aerobically. Prolonged durations of low intensity or high volume training are likely to facilitate recovery and adaptation by promoting autonomic balance and the health of the athlete. Team sport athletes can also benefit from periods of high-intensity interval training, game-based interval training, and plyometrics. Some of the important molecular signals arising from various forms of exercise training include the AMPK and calcium-calmodulin kinases, likely to be activated in response to intense and prolonged exercise, respectively. Both of these signals have similar downstream targets in skeletal muscle that promote development of the aerobic muscle phenotype. Further understanding of how best to manipulate the training programs for future intense exercise athletes and team sportsmen will require the continued cooperation of sport scientists, coaches and athletes alike.

Consensus statements

1) Intense exercise events require a blend of anaerobic and aerobic energy, with the aerobic energy system predominating after near-maximal exercise durations of ~75 s.

2) Short term high-intensity training, typically performed as high-intensity interval training, can elicit improvements in intense exercise performance.

3) Low-intensity, long duration work, or high training volumes, are an important component of successful athletes that perform in intense exercise events, and may facilitate recovery and adaptation from high-intensity sessions by promoting autonomic balance and the health of the athlete.

4) From a metabolic perspective, high training volumes may promote development of the aerobic muscle phenotype through the CaMK signalling pathway, while high-intensity training may affect these adaptations through the AMPK signalling pathway.

5) A polarised training approach where relatively small volumes of high training intensities (~10-15%) are manipulated around large volumes of low intensity training (~75%) appears to be an effective means of enhancing intense exercise performance.

Figure captions


Figure 1. Percent aerobic and anaerobic energy system contributions to near-maximal running over distances ranging from 100 m to 3000 m. Figure derived based on the male data obtained from the studies of Duffield et al. (2004; 2005a; 2005b).

 


Figure 2. Simplified model of the adenosine monophosphate kinase (AMPK) and calcium-calmodulin kinase (CaMK) signalling pathways, as well as their similar downstream target, the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1 α). This ‘master switch’ is thought to be involved in promoting development of the aerobic muscle phenotype. High-intensity training appears more likely to signal via the AMPK pathway, while high volume training appears more likely to operate through the CaMK pathway. ATP, Adenosine Triphosphate; AMP, Adenosine Monophosphate; GLUT4, Glucose Transporter 4; [Ca2+], intramuscular calcium concentration.

Acknowledgements

Special thanks to Iñigo Mujika, Chris Abbiss, Marc Quod and Alison Hall for their helpful comments and editorial assistance during the preparation of this manuscript.

References:

Acevedo EO, Goldfarb AH. Increased training intensity effects on plasma lactate, ventilatory threshold, and endurance. Med Sci Sports Exerc. 1989: 21: 563-568.

Adhihetty PJ, Irrcher I, Joseph AM, Ljubicic V, Hood DA. Plasticity of skeletal muscle mitochondria in response to contractile activity. Exp Physiol. 2003: 88: 99-107.

Baar K. To perform your best: work hard not long. J Physiol. 2006: 575: 690.

Buchheit M, Laursen PB, Al Haddad H, Ahmaidi S. Exercise-induced plasma volume expansion and post-exercise parasympathetic reactivation. Eur J Appl Physiol. 2009: 105: 471-481.

Buchheit M, Laursen PB, Kuhnle J, Ruch D, Renaud C, Ahmaidi S. Game-based training in young elite handball players. Int J Sports Med. 2009: 30: 251-258.

Burgomaster KA, Howarth KR, Phillips SM, Rakobowchuk M, Macdonald MJ, McGee SL, Gibala MJ. Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. J Physiol. 2008: 586: 151-160.

Coffey VG, Hawley JA. The molecular bases of training adaptation. Sports Med. 2007: 37: 737-763.

Costill DL, Thomas R, Robergs RA, Pascoe D, Lambert C, Barr S, Fink WJ. Adaptations to swimming training: influence of training volume. Med Sci Sports Exerc. 1991: 23: 371-377.

Creer AR, Ricard MD, Conlee RK, Hoyt GL, Parcell AC. Neural, metabolic, and performance adaptations to four weeks of high-intensity sprint-interval training in trained cyclists.

Int J Sports Med. 2004: 25: 92-98.

Dudley GA, Tullson PC, Terjung RL. Influence of mitochondrial content on the sensitivity of respiratory control. J Biol Chem. 1987: 262: 9109-9114.

Duffield R, Dawson B, Goodman C. Energy system contribution to 100-m and 200-m track running events. J Sci Med Sport. 2004: 7: 302-313.

Duffield R, Dawson B, Goodman C. Energy system contribution to 400-metre and 800-metre track running. J Sports Sci. 2005: 23: 299-307.

Duffield R, Dawson B, Goodman C. Energy system contribution to 1500- and 3000-metre track running. J Sports Sci. 2005: 23: 993-1002.

Enoka RM, Duchateau J. Muscle fatigue: what, why and how it influences muscle function. J Physiol. 2008: 586: 11-23.

Esfarjani F, Laursen PB. Manipulating high-intensity interval training: effects on VO2max, the lactate threshold and 3000 m running performance in moderately trained males. J Sci Med Sport. 2007: 10: 27-35.

Esteve-Lanao J, Foster C, Seiler S, Lucia A. Impact of training intensity distribution on performance in endurance athletes. J Strength Cond Res. 2007: 21: 943-949.

Esteve-Lanao J, San Juan AF, Earnest CP, Foster C, Lucia A. How do endurance runners actually train? Relationship with competition performance. Med Sci Sports Exerc. 2005: 37: 496-504.

Faude O, Meyer T, Scharhag J, Weins F, Urhausen A, Kindermann W. Volume vs. intensity in the training of competitive swimmers. Int J Sports Med. 2008: 29: 906-912.

Fiskerstrand A, Seiler KS. Training and performance characteristics among Norwegian international rowers 1970-2001. Scand J Med Sci Sports. 2004: 14: 303-310.

Gastin PB. Energy system interaction and relative contribution during maximal exercise. Sports Med. 2001: 31: 725-741.

Gibala MJ, McGee SL. Metabolic adaptations to short-term high-intensity interval training: a little pain for a lot of gain? Exerc Sport Sci Rev. 2008: 36: 58-63.

Gibala MJ, McGee SL, Garnham AP, Howlett KF, Snow RJ, Hargreaves M. Brief intense interval exercise activates AMPK and p38 MAPK signaling and increases the expression of PGC-1alpha in human skeletal muscle. J Appl Physiol. 2009: 106: 929-934.

Hawley JA. Adaptations of skeletal muscle to prolonged, intense endurance training. Clin Exp Pharmacol Physiol. 2002: 29: 218-222.

Hawley JA, Stepto NK. Adaptations to training in endurance cyclists: implications for performance. Sports Med. 2001: 31: 511-520.

Hoogeveen AR. The effect of endurance training on the ventilatory response to exercise in elite cyclists. Eur J Appl Physiol. 2000: 82: 45-51.

Iaia FM, Hellsten Y, Nielsen JJ, Fernstrom M, Sahlin K, Bangsbo J. Four weeks of speed endurance training reduces energy expenditure during exercise and maintains muscle oxidative capacity despite a reduction in training volume. J Appl Physiol. 2009: 106: 73-80.
Iaia FM, Thomassen M, Kolding H, Gunnarsson T, Wendell J, Rostgaard T, Nordsborg N, Krustrup P, Nybo L, Hellsten Y, Bangsbo J. Reduced volume but increased training intensity elevates muscle Na+-K+ pump alpha1-subunit and NHE1 expression as well as short-term work capacity in humans. Am J Physiol Regul Integr Comp Physiol. 2008: 294: R966-974.

Impellizzeri FM, Marcora SM, Castagna C, Reilly T, Sassi A, Iaia FM, Rampinini E. Physiological and performance effects of generic versus specific aerobic training in soccer players.
Int J Sports Med. 2006: 27: 483-492.

Issurin V. Block periodization versus traditional training theory: a review. J Sports Med Phys Fitness. 2008: 48: 65-75.

Laursen PB, Jenkins DG. The scientific basis for high-intensity interval training: optimising training programmes and maximising performance in highly trained endurance athletes. Sports Med. 2002: 32: 53-73.

Laursen PB, Marsh SA, Jenkins DG, Coombes JS. Manipulating training intensity and volume in already well-trained rats: effect on skeletal muscle oxidative and glycolytic enzymes and buffering capacity. Appl Physiol Nutr Metab. 2007: 32: 434-442.

Laursen PB, Shing CM, Peake JM, Coombes JS, Jenkins DG. Interval training program optimization in highly trained endurance cyclists. Med Sci Sports Exerc. 2002: 34: 1801-1807.

Lindsay FH, Hawley JA, Myburgh KH, Schomer HH, Noakes TD, Dennis SC. Improved athletic performance in highly trained cyclists after interval training. Med Sci Sports Exerc. 1996: 28: 1427-1434.

Londeree BR. Effect of training on lactate/ventilatory thresholds: a meta-analysis. Med Sci Sports Exerc. 1997: 29: 837-843.

Lucia A, Hoyos J, Pardo J, Chicharro JL. Metabolic and neuromuscular adaptations to endurance training in professional cyclists: a longitudinal study. Jpn J Physiol. 2000: 50: 381-388.

Mujika I, Goya A, Padilla S, Grijalba A, Gorostiaga E, Ibanez J. Physiological responses to a 6-d taper in middle-distance runners: influence of training intensity and volume. Med Sci Sports Exerc. 2000: 32: 511-517.

Mujika I, Chatard JC, Busso T, Geyssant A, Barale F, Lacoste L. Effects of training on performance in competitive swimming. Can J Appl Physiol. 1995: 20:395-406.

Pyne DB, Mujika I, Reilly T. Peaking for optimal performance: Research limitations and future directions. J Sports Sci. 2009: 27: 195-202.

Rose AJ, Frosig C, Kiens B, Wojtaszewski JF, Richter EA. Effect of endurance exercise training on Ca2+ calmodulin-dependent protein kinase II expression and signalling in skeletal muscle of humans. J Physiol. 2007: 583: 785-795.

Schumacher YO, Mroz R, Mueller P, Schmid A, Ruecker G. Success in elite cycling: A prospective and retrospective analysis of race results. J Sports Sci. 2006: 24: 1149-1156.

Schumacher YO, Mueller P. The 4000-m team pursuit cycling world record: theoretical and practical aspects. Med Sci Sports Exerc. 2002: 34: 1029-1036.

Seiler KS, Kjerland GØ. Quantifying training intensity distribution in elite endurance athletes: is there evidence for an "optimal" distribution? Scand J Med Sci Sports. 2006: 16: 49-56.

Smith TP, Coombes JS, Geraghty DP. Optimising high-intensity treadmill training using the running speed at maximal O(2) uptake and the time for which this can be maintained.
Eur J Appl Physiol. 2003: 89: 337-343.

Smith TP, McNaughton LR, Marshall KJ. Effects of 4-wk training using Vmax/Tmax on VO2max and performance in athletes. Med Sci Sports Exerc. 1999: 31: 892-896.

Stepto NK, Hawley JA, Dennis SC, Hopkins WG. Effects of different interval-training programs on cycling time-trial performance. Med Sci Sports Exerc. 1998: 31: 736-741.

Stepto NK, Martin DT, Fallon KE, Hawley JA. Metabolic demands of intense aerobic interval training in competitive cyclists. Med Sci Sports Exerc. 2001: 33: 303-310.

Vollaard NB, Constantin-Teodosiu D, Fredriksson K, Rooyackers O, Jansson E, Greenhaff PL, Timmons JA, Sundberg CJ. Systematic analysis of adaptations in aerobic capacity and submaximal energy metabolism provides a unique insight into determinants of human aerobic performance. J Appl Physiol. 2009: 106: 1479-1486.

Westgarth-Taylor C, Hawley JA, Rickard S, Myburgh KH, Noakes TD, Dennis SC. Metabolic and performance adaptations to interval training in endurance-trained cyclists. Eur J Appl Physiol. 1997: 75: 298-304.

Weston AR, Myburgh KH, Lindsay FH, Dennis SC, Noakes TD, Hawley JA. Skeletal muscle buffering capacity and endurance performance after high-intensity training by well-trained cyclists. Eur J Appl Physiol. 1997: 75: 7-13.

Yeo WK, Paton CD, Garnham AP, Burke LM, Carey AL, Hawley JA. Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens. J Appl Physiol. 2008: 105: 1462-1470.

Zierath JR, Hawley JA. Skeletal muscle fiber type: influence on contractile and metabolic properties. PLoS Biol. 2004: 2: e348.