Entries in Biomechanics (6)

Wednesday
Nov062013

Visual and auditory / acoustic feedback to optimise rowing technique and boat acceleration

Schaffert's presentation followed on from Matte. Here she saught to bring to the attention of coaches the science behind listening to the boat run. In particular, the causal relationship between movement and sould. He presentation, the Visual and auditory/acoustic feedback to optimise rowing technique and boat acceleration’ looked at this relationship and how a crews perception of it can be enhanced. 

 Key points in Schaffer's presentation: 

- Sonification: The synthetic transformation of data from the boat's movement into sound. 

- The Accrow system used by the German team boats. This creates a specific sound which reacts to each phase and rhytm of the stroke there by creating an intuitive understanding of how the boat is moving. 

The results of which, Shaffer stated that there was a significant increase in mean boat velocity and qyalitative changes in boat acceleration. 

Further reading: 

New Measuring and on Water Coaching Device for Rowing: Klaus Mattes, Nina Schaffert (2010). Provided by the Journal of Human Sport and Exercise online. 

More talks for the Youth Coaching Conference:

Arne Gullich's presentation on Considering long term sustainability in talent promotion – Implications for talent development in rowing.'

Marc Swienty's presentation on the Olympic training centre and rowing boarding school Ratzeburg: Structures and objectives.’ 

Mario Woldt on Actual aspects and considerations of ethics in sport.

Klaus Mattes on: ‘Diagnostic of rowing performance and technique to optimise technique training

Nina Schaffert on: 'Visual and auditory / acoustic feedback to optimise rowing technique and boat acceleration'

 

 

Wednesday
Nov062013

Diagnostic of rowing performance and technique to optimise technique training

We were fortunate enough to have Klaus Mattes present on the topic: Diagnostic of rowing performance and technique to optimise technique training

Mahe Drysdale and Ondrej Synek was used as examples as to how rowers can apply technique under different conditions and importantly, during different segments of the 2000m race, whether it be at the start or in the last 250m. Using the 2013 World Champion, Synek, and the 2012 Olympic Champion, he went onto note how individual characteristics of internationally successful rowing teams can be misinterpreted as "a development of rowing technique".

Mattes explained the following:

- How rowing technique can be tested with the help of biomechanics.

- How results from these biomenchanical measurements can be interpreted.

- Using biomechanical feedback from racing.

Key areas that were identified were:

- Biomechanical measurement such as force angles in the gate, foot stretches and the boat.

- The rowing angle, stroke phases as well as boat velocity.

Using these, Mattes explained that the graphs used from elite German crews highlighted that these different measurements before and after feedback could positively impact on the cure and therefore boat speed.

For more on this topic: 

More talks for the Youth Coaching Conference:

Arne Gullich's presentation on Considering long term sustainability in talent promotion – Implications for talent development in rowing.'

Marc Swienty's presentation on the Olympic training centre and rowing boarding school Ratzeburg: Structures and objectives.’ 

Mario Woldt on Actual aspects and considerations of ethics in sport.

Klaus Mattes on: ‘Diagnostic of rowing performance and technique to optimise technique training

Nina Schaffert on: 'Visual and auditory / acoustic feedback to optimise rowing technique and boat acceleration'

 

Wednesday
Jan042012

Net Power Production & Performance at Different Stroke Rates & Abilities During Sculling 

Constanze Loschner - New South Wales Institute of Sport, Sydney, Australia

Article link: Net Power Production & Performance at Different Stroke Rates & Abilities During Sculling   

Introduction

During on-water rowing, power developed by the rower may be delivered to the oars through the hands and to the foot stretcher through the feet. The proficiency of the rower will be partly determined by the effectiveness with which this power is coupled to boat propulsion. Velocity cost, the average power required to maintain the boat velocity divided by that boat velocity, describes how expensive a rower's technique is in terms of the power delivered in moving the boat through the water. Propulsion is defined as any action that directly affects the forward progression of the boat. For example, the transverse component of the handle force is a necessary accompaniment to the longitudinal component of the total handle force and requires power but has no effect on propulsion. This paper examines the relationship between patterns of power production and absorption and the velocity of the boat.

Methods

Three female international level scullers rowed an instrumented single scull at steady state cadences of 20, 24, 28, and 30 strokes per minute. Scull velocity was measured with a magnetic turbine and pickup coil, pin force with multi-component force transducers, stretcher force with strain gauge transducers, and oar angle with servo potentiometers. This information was sampled at 100 Hz and telemetered to a laptop computer on the shore. Approximately twenty strokes for each rower were time normalised and averaged at each stroke rate. Power delivered to the boat by the rower was calculated as the product of boat velocity and the pin and stretcher forces. Power delivered to the oar handle was calculated as the product of the handle force and handle velocity. Handle velocity was the result of the angular velocity of the oar and linear velocity of the boat. The oar was modelled as a simple lever with the water acting as a fulcrum to calculate handle forces from the pin forces. Motion in the horizontal plane only was considered.

Results & Discussion

For all three rowers power was absorbed by the rower just after the catch but rapidly changes to power generation for the boat, reaching a peak at about 30% of the stroke (Figure 1). The power reaches a second peak during the recovery phase as the rower exerts a propulsive force on the foot stretcher. Power generation during the recovery phase was comparable to power generation during the drive phase.
 
The pattern of propulsive power for rower A is relatively smooth and is generally of lower magnitude in both generating and absorbing modes and especially in the recovery phase, compared with that for rowers B and C.
 
The pattern of power production for rower A resulted in less variable boat velocity (Loschner and Smith, 1999). The smaller the range of the boat velocity the less power required for a given average boat velocity (Dal Monte and Komor, 1989). The mass of Rower B was considerably larger than rower A or C causing a larger drag force on the boat and thus requiring more power output for a given velocity. However rower C was slightly lighter than rower A and a different cause(s) must be found for the poorer performance as measured by velocity cost.

Figure 1 - Total propulsive power delivered to the oar handles and stretcher at
28 strokes per minute for rowers A, B, and C.

Rower C had a relatively irregular propulsive power curve with the largest power absorbing components near the catch. The outcome of this irregularity was a more highly variable boat velocity which in turn required a higher power output for a given average boat velocity. This relativity among the three rowers as described here for a stroke rate of 28 was consistent over the other three stroke rates with differences in the amplitudes of the variables only.

The consistency over stroke rates can also be seen in the values of work efficiency (WE). The values of WE varied among rowers but were constant over the stroke rates. Rower A, although scoring low on velocity cost (VC), obtained the lowest score for WE. WE was the ratio of propulsive work done (the integral of propulsive power over time for one stroke) to the total work done. As the transverse oar handle work done was similar among the rowers this lower value for WE for rower A was due simply to the lower propulsive energy expenditure that was most evident in the recovery phase.

It could be expected that VC would increase with higher BV since the drag force increases exponentially with boat velocity. The power output required for each boat velocity did have a tendency to increase exponentially (Figure 2 below).

Rower A is a world champion junior women's sculler and some of the characteristics of her rowing revealed in this analysis may provide some insight into which techniques make for efficient and effective rowing.

Conclusion

The rowers studied in this project were highly consistent in their work effectiveness over four stroke rates spanning cadences of 20-30. The lower velocity cost achieved by rower A was partly due to a less variable boat velocity produced by a smoother power production. Velocity cost increased with boat velocity.

Studies with larger numbers of rowers in homogeneous groups are required before firm generalisations to other rowers can be made.

Bibliography

Dal Monte A, Komor A (1989) Rowing and Sculling Mechanics. In Vaughan C (Ed) Biomechanics of Sport. Florida: CRC Press. 54-117.
Loschner C, Smith R (1999) The relationship between pin forces and individual feet forces applied during sculling. Proceedings of the Third Australasian Biomechanics Conference. Griffith University, Australia. 31 January-1 February.

Thursday
Nov172011

Comparison of rowing on a Concept 2 stationary and dynamic ergometer

By: Aaron Benson, Julianne Abendroth, Deborah King and Thomas Swensen
Department of Exercise and Sport Sciences, Center for Health Sciences, Ithaca College, Ithaca, NY, USA
Journal of Sports Science and Medicine (2011) 10, 267-273

Article link: Jssm.org



Abstract


Biomechanical and physiological responses to rowing 1000 m at a power output equivalent to a 2000 m race were compared in 34 collegiate rowers (17 women, 17 men) rowing on a stationary and dynamic Concept 2 ergometer. Stroke ratio, peak handle force, rate of force development, impulse, and respiratory exchange ratio decreased by 15.7, 14.8, 10.9, 10.2 and 1.9%, respectively, on the dynamic ergometer. In contrast, percent time to peak force and stroke rate increased by 10.5 and 12.6%, respectively, during dynamic ergometry; the changes in stroke rate and impulse were greater for men than women. Last, VO2 was 5.1% higher and efficiency 5.3% lower on the dynamic ergometer for men. Collegiate rowers used higher stoke rates and lower peak stroke forces to achieve a similar power output while rowing at race pace on the dynamic ergometer, which may have increased the cardiopulmonary demand and possibly reduced force production in the primary movers. Differences were more pronounced in males than females; this dichotomy may be more due to dynamic ergometer familiarity than sex.

Key words: Biomechanics, physiological response, stroke rate, efficiency, cadence.

Introduction


Competitive rowing is a year-round sport that typically includes the use of rowing ergometers for indoor training and as a means to assess fitness across time. Traditional ergometers are stationary; the rower moves relative to the resistance unit. To better simulate on-water rowing, manufacturers developed dynamic ergometers, in which part or all of the ergometer moves in response to the motion of the athlete. Subsequent research comparing dynamic and stationary ergometry to on-water sculling at fixed stroke rates is equivocal. Elliot et al. (2001) showed that dynamic ergometry and sculling elicited similar biomechanics, whereas Kleshnev (2005) observed shorter drive lengths and higher handle forces during ergometry than sculling. In contrast, in studies comparing dynamic and stationary ergometry at fixed work rates, lower stroke forces and higher stroke rates were observed during dynamic than stationary ergometry (Bernstein et al. 2002; Colloud et al. 2006). Despite the observed differences in rowing biomechanics across stationary and dynamic ergometers at fixed work rates, the physiological responses were similar (Bernstein et al., 2002; Mahony et al., 1999).

The aforementioned studies comparing stationary and dynamic ergometers or sculling and dynamic ergometry used the RowPerfect dynamic ergometer. Shortly after the appearance of the RowPerfect dynamic ergometer, Concept 2 developed a unique dynamic ergometer. On the RowPerfect dynamic ergometer, both the seat and foot stretcher move on the main rail, whereas Concept 2 placed its stationary ergometer on “Slides” so that the entire unit moves relative to the motion of the rower (Figure 1). The moving mass on the Concept 2 dynamic ergometer (35 kg) is more than twice as large as the moving mass on the RowPerfect dynamic ergometer (17 kg).

Given the design differences between the two models, it is uncertain if the findings from the studies comparing the RowPerfect stationary and dynamic ergometers are applicable to the Concept 2 counterparts. The primary purpose of this study was to compare the biomechanical and physiological responses of collegiate rowers rowing at a fixed power output representing their 2000m race pace on Concept 2 stationary and dynamic ergometers. Secondary purposes were to determine if there were differences between males and females and between novice and varsity rowers.

Figure 1. Diagram of the catch and finish positions on the stationary and dynamic Concept 2 ergometer.

Methods


Subjects

Forty-five Division III collegiate rowers gave their written informed consent, as approved by the Ithaca College Human Subjects Review Board, and completed the study during the last weeks of a spring rowing season. All rowers had used the Concept 2 dynamic ergometer during the fall and spring seasons of the current racing year; though, based on the coaches’ qualitative assessment, the women’s teams used the dynamic ergometer more so than the men and varsity athletes more so than novice athletes.

Eleven of the rowers were excluded from subsequent data analysis for not maintaining a constant power output between the stationary ergometer (SE) and dynamic ergometer (DE) trials. Power output on the DE had to be within 2% of the power output on the SE. Accordingly, 34 rowers were included in the study, 17 women and 17 men split amongst 12 novice and 22 varsity rowers. Salient subject characteristics are presented in Table 1.

Protocol

Subjects completed two 1000 m trials at their 2000 m race pace on a Concept 2 Model C ergometer (Concept 2 Inc., Morrisville, VT). One trial was completed with the Concept 2 as a SE and the other with the Concept 2 as a DE. Using a counterbalanced design to eliminate order effects, 23 of the original subjects completed the DE trial first and 22 subjects completed the SE trial first. Warm-up on a DE, stretching, and rest between trials were allowed as desired.

Race pace was calculated by determining the power output for each subject based on his or her average 500 m split during a 2000 m ergometer trail. Subjects were instructed to maintain power output during their SE and DE trials at their pre-determined 2000 m race pace power output by watching the ergometer power display. Additionally, a researcher monitoring the power output on the display verbally cued the subject to hold power output steady if it started to fluctuate. The drag factor on the ergometer was set at 130 for all tests; drag factor setting affects the rate at which the flywheel decelerates. With higher settings, the flywheel decelerates more quickly, resulting in greater drag or required effort to achieve a particular power output.

Data collection and analysis

A 2200 N tension load cell (model #3190011, Bertec Corporation, Columbus, OH) mounted between the handle and chain of the ergometer was used to collect handle forces at 1000 Hz using DATAPAC 2K2 software (RUN Technologies, Mission Viejo, CA), an AM6100 amplifier (Bertec Corporation, Columbus, OH), and a PCM-PCMDAS16/330 A/D board (Computer Boards, Inc., Middleboro, MA). The load cell was calibrated by the manufacturer to 216.8 N/V and validated with known static weights. Handle forces were collected on 36 of the original 45 subjects due to data collection time constraints and load cell availability. Of these 36 subjects, only 28 maintained a power output on the DE within 2% of their SE power output. Subject characteristics of the 28 load cell subjects (14 men, 14 women; 11 novice, 17 varsity) are in Table 2.

From the raw force data, stroke rate, stroke ratio, impulse, peak force, time to peak force, and rate of force development were calculated for each stroke during the last minute of rowing. The catch of each stroke was identified as the point at which force increased above a 10 N threshold, and the finish was the point at which force dropped below 10 N. The drive phase was defined as the time between catch and finish. The recovery phase was defined from the finish of the drive to the next catch.

Stroke ratio was calculated as recovery time divided by drive time. Impulse was the integral of force from catch to finish. Peak force was the maximum force recorded during each stroke. Time to peak force was the time in seconds from the catch to peak force. Time to peak force was also expressed as a percent of stroke time. Rate of force development was calculated by dividing peak force by time to peak force in s. The average of each variable was calculated across strokes from the last minute of rowing and used for all subsequent analyses. The ergometer measured and stored the average power output and stroke rate for each trial. Since it takes two to four minutes to achieve a physiological steady state while rowing at a constant pace, the physiological data were also measured over the last minute, or at the end of trial, depending on the variable (Hagerman 1984). Expired gases were measured with a ParvoMedics True-Max2400 metabolic cart (Consentius Technologies, Sandy, UT), which was recalibrated for every test. The cart used expired gasses to calculate VO2 and the respiratory exchange ratio (RER) every five seconds; the 12 samples preceding trial termination were averaged to obtain data for the final minute. Rowing efficiency (W⋅L-1⋅min-1) was calculated by dividing the average power by absolute VO2 from the final minute of a trial. Heart rate (HR) was tracked throughout a trial with a Polar F1 heart rate monitor (Polar Electro Inc., Lake Success, NY). The maximum HR observed during the final minute was recorded for data analysis. Immediately after each trial, participants rated total body and lower extremity rating of perceived exertion (RPE) on the modified BORG scale (1-10).

Statistical analysis

Power output was evaluated for the SE and DE trials of each subject. Subjects whose DE power output was not within 2% of their SE trial were excluded from the study and not used in the statistical analysis. Biomechanical and physiological variables were analyzed with a mixed model 2 × 2 × 2 ANOVA (ergometer: stationary v. dynamic × sex: male v. female × experience: novice v. varsity) with repeated measures on ergometer at an α-level of 0.05. Significant interactions were explored using independent or dependent t-tests as appropriate. Sidak-Bonferroni adjustments were made to the alpha level for the multiple pairwise comparisons (Sidak, 1967). As suggested by Neter, et al. (1996), the number of pairwise comparisons depended on the specific interaction resulting in new α-levels of 0.0253 for two pairwise comparisons and 0.0127 for four pairwise comparisons. All analyses were performed with SPSS software (SPSS Inc; Chicago, IL).

Results


There were no differences between novice and varsity athletes for any of the measured variables, and thus all data were combined across experience level. Subsequent analyses used 2 × 2 ANOVAs with repeated measures on ergometer to compare differences across ergometer design and between men and women only. Row times were similar between the SE and DE, 220.9 ± 19.6 s and 220.6 ± 19.6 s, respectively. Accordingly, mean power outputs were also similar between SE (272.2 ± 72.2 W) and DE (272.9 ± 72.2 W). Effect sizes for all comparisons were extremely small ranging from 0.01 to 0.05 (Cohen 1969). Dependent t-tests with a Sidak-Bonferroni adjusted alpha level of 0.0083 for the six multiple comparisons revealed no significant differences (p ranging from 0.025 to 0.508) in power output for the SE and DE for all groupings of subjects. Power output for the men was 58% greater than for the women (p < 0.001). In the load cell subgroup, power output for the men was 48% greater than for the women (p < 0.001). These differences decreased when power output was normalized to body mass, with men producing 31% and 28% more power per kg than the women for all subjects and the load cell subjects respectively (p < 0.001). Power outputs in Watts are presented in Table 3.

Biomechanical variables

The 28 rowers in the load cell analysis group were similar in age, height, mass, and years of experience as compared to the entire 34 rowers as determined with independent t tests (p > 0.278 all variables). Moreover, there was no significant difference between experience level (p = 0.752) between the men and women of this subgroup; though, height and mass were significantly different between the 14 males and 14 females (independent t-tests, p < 0.001 both variables).

There was no difference (p = 0.532) in stroke rate, measured in strokes per minute (spm) between the men, 30.6 ± 3.2 spm, and women, 30.1 ± 2.4 spm. Stroke rate was 12.6% higher on the DE (p < 0.001); the change in stroke rate was greater for the men, 15.5%, than for the women, 9.8%, (p = 0.026). Stroke ratio was 0.34 lower on the DE than the SE (p < 0.001). Impulse and peak handle force were 67 and 36% greater for the men than women, respectively (p < 0.001 both variables). Both impulse and peak force were lower (p < 0.001 both variables) on DE than the SE, decreasing 10.2 and 14.8%, respectively. The drop in impulse, 44.6 N·s for the men and 21.1 N·s for the women, was greater for men than women (p < 0.001). Absolute time to peak force, expressed in seconds, did not change across ergometers (p = 0.609); however, when expressed relative to stroke time, percent time to peak force occurred 1.2% later in the stroke (p < 0.001) on the DE, 15.3 ± 2.2%, than on the SE, 13.8 ± 3.0%. Rate of force development (RFD) was 12% lower on the DE as compared to the SE (p = 0.006). Moreover, RFD was greater (p < 0.001) for the men, 3053 ± 726 N·s-1, than for the women, 2196 ± 511 N·s-1. Table 4 shows the biomechanical data and Figure 2 depicts the average force profiles separated by ergometer and sex.

Physiological variables

Table 5 shows the physiological data. Heart rate was 1.7% lower for males as compared to females (p = 0.008). Absolute and relative VO2 were higher during DE than SE (p ≤ 0.017); this difference resulted from the changes in the men, whose VO2 was 0.24 L·min-1 or 2.80 ml·kg-1· min-1 higher on the DE than SE (p ≤ 0.007). There was no difference in VO2 for the women between ergometers.

The women did have lower absolute and relative VO2 than the men on both machines (p < 0.001). Men were 8.3 W·L-1·min-1 more efficient than women on the SE (p = 0.003). Male efficiency dropped 2.3 W·L-1·min-1 on the DE relative to the SE (p = 0.018). Total body and lower extremity RPE were similar on the DE (7.5 ± 1.4 and 7.1 ± 1.5, respectively) and SE (7.6 ± 1.0 and 7.4 ± 1.2, respectively), and RER was 1.9% lower on the DE than the SE (p = 0.016).

Discussion


The primary purpose of this study was to compare the biomechanical and physiological responses of collegiate rowers at a constant 2000 m race pace power output on a Concept 2 stationary and dynamic ergometer. Stroke rate and percent time to peak force were higher at fixed workloads during dynamic ergometry than during stationary ergometry. In contrast, stroke ratio, impulse, peak force, and RER were lower during dynamic than stationary ergometry. Secondary purposes were to investigate differences between novice and varsity rowers and between male and female rowers. Males had overall higher power outputs accompanied by higher peak handles forces and impulses than the females. The lack of effect of experience, novice v. varsity, observed in this study could be related to the end of the season data collection. One year of on-water and ergometry rowing may have sufficiently minimized differences in the physiological and biomechanical variables measured during SE and DE ergometry in the novice and varsity athlete. Alternatively, it is possible that constraints of ergometry rowing minimize technique and physiological differences between novice and varsity rowers that may be present during on-water rowing.

Biomechanical variables

Stroke rates were similar on the stationary ergometer between males and females and increased an average of 12.6% on the dynamic ergometer when maintaining a fixed power output. The higher stroke rate observed on the Concept 2 dynamic ergometer is similar in magnitude to the increase previously measured on the RowPerfect dynamic ergometer relative to its stationary model (Bernstein et al., 2002). Stroke ratio also decreased 13.5 and 17.8% for women and men respectively during dynamic ergometry due to a drop in recovery time; drive time was similar for all subjects across ergometers (approximately 0.67 s). These results support findings that show increases in stroke rate are accomplished by decreases in recovery time (Dawson et al., 1998; Torres-Moreno et al., 2000). The increase in stroke rate from stationary to dynamic ergometry in the current study was larger for men than women (15.5 vs. 9.8%, respectively). According to the coaches, the female rowers utilized the dynamic ergometers more frequently during practice than the male rowers. The additional training may have enabled the female rowers to apply force more effectively during dynamic ergometry, resulting in fewer strokes per minute to obtain their specified power output as compared to the men. The larger decrease in impulse for men (12.0%) on the dynamic ergometer than women (7.7%) substantiates this supposition. To maintain power output, the men’s larger drop in impulse was counterbalanced by a greater increase in stroke rate on the dynamic ergometer, while the women, who had a smaller drop in impulse on the dynamic ergometer, did not have as large an increase in stroke rate. Due to the purported disparity in dynamic ergometry use by the male and female rowers in this study, the result may reflect additional experience on the dynamic ergometer as opposed to inherent sex differences.

Peak handle forces were also lower on the dynamic ergometer than on its stationary counterpart when rowing at fixed power outputs; these differences are consistent with changes seen on the RowPerfect dynamic ergometer relative to its stationary model (Bernstein et al. 2002; Colloud et al. 2006). Peak handle force data are similar to the handle force data observed during on-water rowing in an eight, which suggests that the Concept 2 dynamic ergometer approximates on-water rowing conditions in such boats (Ishiko et al., 1983; Zatsiorsky and Yakunin, 1991). The dynamic ergometer peak handle force and impulse data of the current study are, however, approximately 20% lower than those reported in a study of brief duration maximum rowing on a Concept 2 DE (Benson and Abendroth-Smith, 2004). The differences in impulse and peak force between the studies are expected given the different work tasks. The subjects in the Benson and Abendroth-Smith (2004) study, also Division III collegiate rowers, generated maximum power output in 20 strokes, whereas the subjects in the current study completed 1000 m pieces at their 2000 m race pace. The subjects in the 2004 study likely used stroke force to increase power output, as opposed to relying on stroke rate alone or a combination of stroke rate and stroke force, to maximize power output. Time to peak force, stroke ratio, and stroke rates were similar between the current study and the Benson and Abendroth-Smith (2004) study.

While absolute time to peak force was similar across ergometers in the current study, percent time to peak force increased from stationary to dynamic ergometer. More importantly, rate of force development was lower on the dynamic ergometer. The lower peak force and lower rate of force development are visually evident from the force-time profiles (Figure 2).

Also apparent on the force curves, though not quantified, is a more drastic change in slope, or RFD, approximately 10% into the stroke cycle on the dynamic ergometer. This apparently steeper slope just following the catch transitioning to a lower RFD before peak force is consistent across rowers and has been observed in other studies for both on-water and dynamic ergometry rowing (Bernstein et al., 2002; Elliot et al., 2001; Martindale and Robertson, 1984).

Kleshnev and Kleshneva (1995) proposed that the absence of the change of slope between the catch and peak force on a stationary ergometer may be due to disparity between foot stretcher and handle force. Alternatively, the subtle differences in RFD between the ergometers could be due to the smaller ergometer mass being accelerated on the dynamic ergometer, which is approximately 35 kg for the Concept 2. On the stationary ergometer, in contrast, the rower accelerates his or her body mass with each stroke, which was 69.0 ± 7.2 kg and 80.0 ± 10.0 kg for the women and men, respectively. The lighter mass may allow forces to be developed more quickly just after the catch and may better approximate the mechanics of on-water rowing, which may be advantageous for offwater training for competitive rowers. Collectively, the biomechanical data reported in this and other rowing studies show that athletes pull more strokes per minute with less force per stroke on a dynamic ergometer compared to its stationary counterpart at a fixed power output (Bernstein et al., 2002; Colloud et al., 2006). The reduced force per stoke observed on the dynamic ergometer may reflect a decreased effectiveness at transferring propulsive force during dynamic ergometry. The force change requires rowers to pull more strokes per minute to maintain the same power output, which they do by decreasing recovery rather than drive time (Dawson et al., 1998; Torres-Moreno et al., 2000). All the aforementioned biomechanical differences allow dynamic ergometry to better simulate actual rowing or sculling (Elliot et al., 2001; Kleshnev, 2005).

Physiological data

The increased VO2 and decreased efficiency on the dynamic ergometer for the men rowing at a fixed power output may be a consequence of the stroke rate change. Similar changes in VO2 and efficiency or economy occur as cadence increases at various power outputs in trained to well-trained male cyclists (Chavarren and Calbret, 1990; Coast and Welch, 1985; Hagberg et al., 1981; Marsh and Martin, 1997; Nielsen et al., 2004; Takaishi et al., 1998). The VO2 changes in the male subjects in the current study, however, contrast with data from an earlier rowing study, which showed that VO2 was similar during incremental tests to exhaustion on a RowPerfect stationary and dynamic ergometer in elite male rowers (Mahony et al., 1999). The inconsistency in VO2 data between the current study and Mahony et al. (1999) may be due to differences in subject fitness and dynamic ergometer familiarity. Indeed, VO2 was similar across conditions for the female subjects in this study, who were more highly ranked than the male subjects, and, who like the subjects in Mahony et al. (1999), were more experienced on the dynamic ergometer. Data from cycling studies support the hypothesis that subject fitness and dynamic ergometer experience affect VO2 as stroke rate increases at a fixed power output. The cycling data show that VO2 increases to a greater extent in less experienced and less fit males at higher cadences across various power outputs than it does in more fit and more experienced males (Marsh and Martin, 1993; 1997; Takaishi et al., 1998). A possible explanation for the 5.0% increase in VO2 in the male rowers in this study during dynamic ergometry is that they had to increase internal muscular work to achieve the specified workload. Perhaps the males’ relative inexperience with the dynamic ergometer required them to increase synergist and core muscle activation to produce the specified power output during dynamic ergometry. Data from cycling studies support this supposition and show that inexperienced males have higher muscle EMG as cadence rises across various power outputs than experienced male cyclists (MacIntosh et al., 2000; Takaishi et al., 1998).

The difference in RER between conditions in the subjects in this study was 1.9% with a small to moderate effect size of 0.3, suggesting a small but possibly meaningful change. RER values above 1.00, as seen in both conditions, indicate increased buffering of plasma lactate, and correspond to elevated levels of anaerobic metabolism in the working musculature (Brooks at al., 2000). The small but significantly lower RER on the dynamic ergometer relative to its stationary counterpart at a fixed power output suggests that anaerobic ATP production was reduced during dynamic ergometry, reflecting a possible decrease in metabolic activity in the primary movers, a supposition supported by the lower impulse and peak handle forces measured during dynamic ergometry.

Lower extremity RPE data are inconsistent with the aforementioned hypothesis. The most probable explanation for the lack of change across ergometers in lower extremity RPE specifically, and whole body RPE generally, is that the subjects based their perceived exertion primarily on intensity, which was similar across trials. Since the subjects trained regularly at that intensity, they probably had well-formed notions of how they should feel after a 1000 m work bout. In short, the sensitivity of the RPE scale may be insufficient to measure potentially small but significant changes as were observed in VO2 and RER.

Collectively, physiological data show that the cardiopulmonary load was greater during dynamic ergometry at a fixed power output in some subjects; the data also suggest that anaerobic metabolic activity in the primary movers was reduced. These changes likely resulted from the higher stroke rates needed to produce the same power output while rowing on the dynamic ergometer. These findings are consistent with the literature on cyclists, which shows that greater exercise cadences reduce primary mover force production and increase aerobic demand (Chavarren and Calbret, 1990; Coast and Welch, 1985; Hagberg et al., 1981; Marsh and Martin, 1997; MacIntosh et al., 2000; Moritani and Muro, 1987; Nesi et al., 2004; Nielsen et al., 2004; Sparrow et al., 1999; Takaishi et al. 1998).

Together, the findings suggest that biomechanical and physiological changes occur in dynamic ergometry compared to stationary ergometry at constant power outputs Decreases in peak handle force and impulse on the dynamic ergometer were accompanied by increases in stroke rate between ergometers. It is possible that some of these differences were a product of the experimental design, which allowed stroke rate to vary across ergometer as the subjects rowed at a constant power output. Consequently, in future studies comparing stationary and dynamic ergometers, scientists may wish to control both power output and stroke rate to determine if there are genuine differences in the biomechanical and physiological response between the two designs. Future studies should also examine stationary and dynamic ergometry under race conditions to determine if either ergometer results in a greater power output over a fixed distance and elicits different biomechanical adaptations and physiological responses. The biomechanical and physiological changes in this study may also have been influenced by experience and training time on the dynamic ergometer, which was not controlled. The larger changes in impulse and stroke rate accompanied by a larger increase in VO2 and drop in efficiency for the males was confounded by the men being not as experienced with dynamic ergometry nor as accomplished rowers as the females. Thus, it is difficult to determine the root cause for the less effective force application and increased cardiopulmonary demand observed in the male subjects on the dynamic ergometer. Future studies should examine stationary and dynamic ergometry following a season of standardized training on the stationary and dynamic ergometers.

Conclusion


Collegiate rowers used higher stoke rates and lower stroke forces to achieve a similar power output on the dynamic Concept 2 ergometer than its stationary counterpart. These changes increased the cardiopulmonary demand in some rowers and possibly reduced force production in the primary movers. The differences were more pronounced in males than females; this dichotomy may be due to dynamic ergometer familiarity more than sex. These results have important implications for athletes training on Concept 2 stationary and dynamic ergometers. Depending on the athlete, stationary and dynamic ergometry may be equally useful for cardiopulmonary fitness, stationary ergometry may best improve force production, and dynamic ergometry may help rowers maintain their feel for the water with more similar force profiles and high stroke rates.

Key points

• When rowing at a constant power output, all rowers used higher stroke rates and lower stroke forces on the Concept 2 Dynamic ergometer as compared to the Concept 2 Stationary ergometer.

• When rowing at a constant power output, cardiopulmonary demand was higher for all rowers, as measured by heart rate, on the Concept 2 Dynamic ergometer as compared to the Concept 2 Stationary ergometer.

• When rowing at a constant power output, efficiency was lower for male rowers on the Concept 2 Dynamic ergometer as compared to the Concept 2 Stationary ergometer.

Acknowledgment


This paper is dedicated to the memory of Julie Abendroth.

References


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Thursday
Nov102011

Rowing Biomechanics

By: Dr Valery Kleshnev (2006):
Rowing Science Consultant
Managing Director, Biorow Ltd

Direct links to Rowing biomecanics news letters, see Biorow and High Performance Rowing Recources.


History

Rowing is one of the oldest human activities and known for more than 5,000 years. Rowing in cane boats by means of long oars can be seen on frescoes from the 5th Dynasty of the Pharaohs in Egypt in 2500 B.C. Rowing races in various types of boats were popular in ancient Greece and Rome. Though rowing was not in the program of ancient Olympic Games, there were evidence that more than 100 boats and 1900 oarsmen participated in rowing regattas organized by Emperors Augustus and Claudius Dal Monte, 1989).

Rowing became popular sport in Europe since the XVII century. The oldest of the currently existing “The boat race” between teams of Ojxford and Cambridge Universities began in 1829. In XIX century races of professional scullers collected multi-thousand crows on banks of the Thames River and millions of pounds were spent on betting, which resembles popularity of modern boxing, tennis and Formula-1 car racing.

International Rowing Federation FISA was founded in 1892. FISA is the oldest international sport federation. Now it includes representatives if 118 National rowing associations.

Rowing is the oldest Olympic sport. Though rowing competition was not held on the first Games in Athens in 1896 due to bad weather conditions, it has always been in the program of the modern Olympic Games. Currently, presence of sports and athletes is limited in Olympic Games. There is very tough competition for a quote. However, rowing managed to maintain the third large quote after athletics and swimming having 14 medals sets and more than 550 athletes participating.

In 2005 adaptive rowing was included in Paralympics, which is also evidence of its growing popularity.

Trends of rowing performance

Long term performance in rowing is difficult to analyse, because it is significantly affected by weather conditions and differences over the courses used during European, World and Olympic events. A more detailed presentation of the progress maybe obtained by comparison of the records from a single regatta and, for that purpose, the Royal Henley Regatta is ideal, because it is the oldest still existing institution in race rowing. It is possible to define the following periods of rowing development, which can be seen on Figure 1:

 

Figure 1. Trend of rowing speed based on records of the Grand Challenge Cup (M8+) of the Royal Henley Regatta

Before 1900 there was a fast growth of performance of 1-1.5% per year, which may be explained by initial development of equipment (timber boats, outriggers, and the sliding seat), in addition to sporting technique and training methods.

The slower growth of ?0.5% per year from 1900 – 1950 may have been caused by the two World Wars, the amateur status of the athletes and the relatively limited competition due to the separation of sport organisations between the East and West political alliances.

However, from 1950 – 1980 performance grew at very fast pace of ?1-2% per year. It can be considered that when Eastern block countries joined Olympic sport in 1952 the competition level was substantially raised. Thus, sport became a political factor and a professional activity, which boomed the training volume, methods and use of drugs in sport. This performance growth was even faster in women, because it coincided with initial development in women’s events.

In the period of 1980 – 1996 there has been a slower growth of ~0.5-0.8% a year. This growth rate could be reflective of the training volume approaching its biological limit; an improvement of the drug control. Rowing performance, however, continues to grow relatively faster than in athletics and swimming. We can speculate that the reasons were equipment development (plastic boats and oar s replaced wooden ones, introduction of the "big blade”) and active FISA position in wider promoting of rowing and popularisation of modern training technologies.

1996 – now. Stable period and even decreasing of performance. We can speculate that the reasons could be further development of doping control methods (such as blood doping test) and sociological factors.

Boat types and rowers’ categories

From its origin up to the 1972 Games rowing had seven male events in Olympic program (1x, 2x, 2-, 2+, 4-, 4+, 8+ on the standard distance 2000 m). In 1976 a number of events was increased to 14: one male event (4x) and six female events (1x, 2x, 4x, 2-, 4-, 8+ on the distance 1000 m) were introduced. Women events changed the distance to the standard 2000m in 1984, which have made female rowing more aerobic with less demand for strength and power. The current Olympic program was introduced after the 1992 Games, when lightweight events were included (LM2x, LM4-, LW2x) on the expense of (M2+, M4+, W4). Yet, these events are included in the World Championships Program. (Table 1)

Boat Type

Men

 

Women

 
 

Heavyweight

Lightweight

Heavyweight

Lightweight

Single scull (1x)

OG

WC

OG

WC

Double scull (2x)

OG

OG

OG

OG

Quad scull (4x)

OG

WC

OG

WC

Pair (2-)

OG

WC

OG

 

Four (4-)

OG

OG

WC

 

Eight (8+)

OG

WC

OG

 

Pair with coxswain (2+)

WC

     

Four with coxswain (4+)

WC

     

 

Table 1. Rowing events in Olympic Games (OG) and World Championships (WC) programs. 

Rigging

Gearing

In sports such as rowing and cycling the term “gearing” is used for a ratio of the velocities of locomotion to the velocity of athlete action. According to the lever law, the ratio of forces is reversely proportional to the ratio of velocities. Athletes, therefore, have to apply proportionally more force as the gearing decrease velocity of their action at constant speed of locomotion. In rowing the gearing is defined by two main variables: oar length versus the inboard length (Figure 2).

Figure 2. Oar gearing variables

The oar length is measured from the handle top to the outer edge of the blade in the line of the shaft. The inboard is measured from the handle top to the face of button. However, actual resultant forces are applied to different points of the blade:

• Point of the handle force application is difficult to locate exactly and it may vary in different rowers. We assume that the handle force is applied at the centre of the handle, which is located 6 cm from the handle top in sculling and 15 cm – in sweep rowing.
• Gate force applied to the centre of the pin, which offsets from the button on the half width of the gate and it is usually 2cm.
• Blade force applied to the centre of water pressure on the blade. It is even more difficult to define and it may vary depending on the angle of attack. We assume it applied at geometrical centre of the blade, which usually located 20 cm from the outer edge in sculling and 25 cm in sweep rowing.

Table 2. Oar gearing (based on Nolte, 2005) and corresponding speed characteristics (based on the World best times for 2006) in different boat types.

Boat Type

Oar Length (m)

Inboard (m)

Actual Inboard (m)

Actual Outboard (m)

Actual Gearing

Boat speed, men (m/s)

Boat speed, women (m/s)

Handle speed, men (m/s)

Handle speed, women (m/s)

1x

2.88

0.88

0.84

1.78

2.119

5.05

4.68

2.38

2.21

2x

2.88

0.88

0.84

1.78

2.119

5.49

5.02

2.59

2.37

4x

2.89

0.875

0.835

1.795

2.150

5.92

5.39

2.76

2.51

2-

3.72

1.16

1.03

2.29

2.223

5.34

4.83

2.40

2.17

4-

3.73

1.15

1.02

2.31

2.265

5.86

 

2.59

 

8+

3.73

1.14

1.01

2.32

2.297

6.25

5.61

2.72

2.44

 

Actual gearing is heavier in sculling than in sweep boats. The variation is small between small and big boats and does not correspond to the difference in the speed of the boat. The difference in the handle speeds between 1x/2- and 4x/8+ is quite significant (12-14%). This leads to the variation of the racing rate, which varies from 34-36str/min in 1x/2- to 39-40 str/min in 4x/8+. Actual gearing is higher (heavier) at the catch and finish of the drive than at the perpendicular position of the oar. At catch and finish the blade moves at the angle to the boat movement and its longitudinal component equal to cosine of the angle. E.g. at the catch angle of 60o the gearing is two times heavier and at 45o it is 30% heavier than at the perpendicular oar position.

Rower’s workplace

It is important to setup the rower’s workplace properly, because its geometry affect vectors of forces and velocities and, hence, efficiency and effectiveness of rowing technique.

  Figure 3. Variables of the rower’s workplace geometry

The main variables are:
• Gate height is measured from seat to the bottom of the oarlock and varies from 14 to 19cm depending on the rower’s height. In sculling the left gate usually 0.5-2 cm higher than the right one.
• Heels depth is measured from seat to the bottom of the shoes and varies from 15 to 22 cm depending on the rower’s body composition.
• Seat height from water varies depending on boat type and weight of the rowers.
• Span in sculling is measured from pin to pin. Spread in sweep rowing is measured from pin to the boat centreline. Usually, the inboard length is longer than the spread in sweep boats or half of the span in sculling boats. This makes overlap measured between tops of the handles in sculling, which is usually 15-20 cm, and between the boat centreline and top of the handle in sweep rowing of 25-30 cm.
• Stretcher position is measured from the pin to the toes of the shoes and is 50-65 cm.
• “Work through” is the distance from the pin to the end of the slides and is 5-12 cm.
• The distance that the seat travels is usually 60-65 cm.
• Stretcher angle varies from 36o to 45o.
• Slides angle is usually set between 0.5o and 1.5o.
• Oar pitch is the angle between vertical line and the blade. In depends on two settings: pitch of the blade relative to the sleeve and the gate pitch. The first one usually set to zero and the second one varies between 2o and 6o. If the pin is leaning inwards, then the pitch at catch will be less and at finish more than it the perpendicular position of the oar. Outwards leaning of the pin produce the opposite changes in the pitch. Usually, the pin is set vertically, but some coaches use 1o-2o outward leaning of the pin, which prevents the blade from going too deep at the catch and too shallow at the finish of the drive.

Mechanics

Propulsion and blade efficiency

When the rower applies force to the oar handle (Fhandle), it is transferred to the blade and applies pressure on the water. According to Newton's 3rd law this creates reaction force on the blade Fr.blade, which is the force that accelerates the rower-boat-oars system (RBOS) forward. During the drive phase, the centre of mass (CM) of the whole system moves forward and the centre of pressure (CP) of the oar slips through the water. Some point on the oar shaft remains stationary and can be considered as an imaginary fulcrum. It is not a real fulcrum because there is no support at this point. The position of the fulcrum changes during the drive phase and depends on the blade propulsive efficiency: the higher the efficiency, the closer fulcrum to the CP of the blade. The fulcrum coincides with CP at 100% efficiency.

Figure 4. Forces in the rower-boat-oar system

Reaction force on the blade is the sum of the drag and the lift forces. As an angle of attack changes through the drive, the ratio of the drag and lift forces changes from 1:2 the angle 60deg at catch to 1:0 at the oar position perpendicular to the boat (Caplan and Gardner, 2005). The lift force does not result in any loss of energy, i.e. it is 100% efficient, because vectors of force and velocity are perpendicular to each other. The vector of the drag force is parallel to the velocity vector and has opposite direction. Waste of energy is calculated as a scalar (dot) product of blade force and velocity vectors. Propulsive power is the product of the force and velocity vectors applied to the CM of RBOS. The sum of the propulsive and the waste posers equals the total power applied to the oar handle. Propulsive efficiency of the blade is a ratio of the propulsive power to the total power. Propulsive efficiency of the blade can be derived by means of measuring instantaneous boat velocity, oar angle and a force at the oar handle or gate (Affeld, 1993, Kleshnev 1999). The force applied to the oar blade (Fb) is calculated using measured handle force and oar gearing. The blade velocity (vb) is derived using oar angle and boat velocity data.

Figure 5. Path of the oar during the stroke cycle

Propulsive efficiency of the blade depends on the relative pressure on the blade, i.e. the ratio of the blade force to the blade area. Lower pressure relates to less slippage of the blade through the water and higher blade propulsive efficiency. To increase efficiency there is a need to reduce blade force or to increase the blade area. The blade force is reduced at the same handle force by means of changing the oar gearing ratio to heavier values (shorter inboard and longer outboard distance). However, very heavy gearing will decrease muscular efficiency of the rower, because the handle speed will decrease and it makes muscles work in slow static-like regimen. Increasing of the blade area is also limited because wider blade takes more time and requires more effort for entry and extraction from the water. A very long blade is also inefficient, because it can create counter-movement effect on opposite sides of the blade. Also, the blade efficiency is affected by the velocity of the boat, and it is higher in faster (bigger) boat types. Sculling has a higher blade efficiency than sweep rowing, which can be explained by higher sum of the blade area. This could be one of the reasons why sculling boat are faster than sweep boats of the same size. The characteristics of the force application affect blade efficiency and may be controlled by the rower. A force curve with a peak increases blade slippage and decreases efficiency. Conversely, a rectangular shape of the force curve affects efficiency positively. There is a moderate correlation between the ratio of average to maximal force, taken as a measure of the shape of the force curve (100% for rectangle, 50% for triangle), and blade efficiency (r = 0.48, p<0.01).

Table 3 Average values of the blade propulsive efficiency based on 1470 crew-samples collected during 1998-2005 in the Australian Institute of Sport (AIS).

 

Men

Woman

Average

Boat Type

Heavy

Light

Heavy

Light

 

1x

79.6%

 

78.5%

 

79.0%

2

78.5%

 

80.6%

 

79.4%

2x

82.3%

81.9%

83.6%

84.1%

83.0%

4-

80.2%

82.1%

80.5%

 

81.0%

4x

83.7%

 

87.3%

 

85.5%

8-

81.4%

 

81.5%

 

81.4%

 

Bigger boats have higher blade efficiency due to higher average speed, which makes lift force more significant. Scullers are efficient because of the bigger total area of the blade. Higher blade efficiency in lightweight women’s crews can be explained by lower force application, which relates to lower relative pressure on the blade and less slippage through the water.

The Vortex Edge blade was introduced in attempt to increase efficiency (Concept 2 web site). The overall improvement of the blade efficiency with Vortex is about 2%. Application of the Vortex shifts the centre of pressure towards the outer edge of the blade, equivalent to increasing the outboard lever of the oar.

Boat Speed: Resistance, Variation, Efficiency

According to fluid dynamics drag resistance force is proportional to the square of boat speed and drag power is proportional to the cube of the velocity. Therefore, if a crew increase the boat speed twice, then they should overcome four times higher drag force and apply eight times more power. Normally, the hydrodynamic resistance of the water represents 85% of the total drag force, which includes 70% water friction, 10% wave resistance and 5% pressure resistance. Aerodynamic resistance normally represents 15%, but at head wind it increases up to 30% at wind speed of 5 m/s and up to 50% of total drag at 10m/s. Correspondingly, in tail wind, air resistance decreases to 0% at wind speed equal to the boat speed. Rowers’ bodies create approximately 75% of air resistance, oars give nearly 20%, and the remaining 5% depend on the boat hull and the riggers. Strait head wind is beneficial for big boats, because the bow rower shields the rest of the crew, which decrease the drag. Cross-head wind has less influence on small boats (Figure 6).

Figure 6. Boat speed at strait (a) and cross (b) winds (Filter, 2000);

Water viscosity decreases at higher water temperature, which decreases hydrodynamic resistance and allows higher boat speeds

Figure 7. Boat speed at different water temperature (Filter, 2000);

Due to the periodic nature of the drive phase in rowing, the boat speed is not constant during the stroke cycle (Figure 8, a). The drag power increases more at a higher than average boat velocity (dash shaded area on Figure 8, a), than it reduces at a lower than average velocity (cross shaded area). The total energy expenditure at variable boat velocity is, therefore, higher compare with constant velocity.

 Figure 8. Deviations ofthe shell velocity and drag power from agerage (a); and Ratio Recovery and Drive (b)

The ratio of the minimal power required to propel the boat at a given constant speed to the actual propulsive power at variable boat velocity is called “Boat efficiency”.
Table 4. Boat Efficiency of rowing in Olympic boat types.

 

Men

Woman

Average

Boat Type

Heavy

Light

Heavy

Light

 

1x

95.1%

 

94.5%

 

94.8%

2-

94.9%

 

95.1%

 

95.0%

2x

94.9%

95.5%

95.4%

96.3%

95.5%

4x

96.2%

 

95.6%

 

95.9%

4-

95.4%

95.3%

91.9%

 

94.2%

8+

96.4%

 

96.5%

 

96.4%

 

For improvement of the boat’s efficiency Sanderson and Martindale suggested optimisation of the rowers’ movement on recovery to maintain the shell speed as constant as possible. In high stroke rates the recovery time is shorter and that dictates faster movement of the rowers’ mass and higher acceleration of the shell. Therefore, the boat velocity fluctuations increase with stroke rate (a), which leads to a decrease of the boat velocity efficiency (b) and stroke rate has a negative correlation with the boat efficiency (r = -0.34, p < 0.05). On average, the boat efficiency drops 1.4% from stroke rate 20 (96.0%) to 40 (94.6%).

Table 5. Boat Efficiency of rowing in Olympic boat types.

 

Men

Woman

Average

Boat Type

Heavy

Light

Heavy

Light

 

1x

95.1%

 

94.5%

 

94.8%

2-

94.9%

 

95.1%

 

95.0%

2x

94.9%

95.5%

95.4%

96.3%

95.5%

4x

96.2%

 

95.6%

 

95.9%

4-

95.4%

95.3%

91.9%

 

94.2%

8+

96.4%

 

96.5%

 

96.4%

 

Newton's Laws of Motion, Kinetic Energy, Centre of Mass

The implication of Newton’s first law is that rowers have to apply force to overcome drag and maintain linear movement of the boat. When force is applied to the blade during the drive phase, an equal and opposite directed reaction force is created, according to the third Newton law. The forward component of this reaction force is the only reason of acceleration of the boat’s centre of mass.

According to Newton’s second law, the magnitude of this acceleration is proportional to the mass of the system and the magnitude of the propulsive force.

When the CM of the boat accelerates, it accumulates kinetic energy, which is spent on overcoming drag resistance and lost as heat to the surroundings of the rowing boat.

However, rowing mechanics is not as simple as it looks. It may appear that the main target of the crew is acceleration of the boat and because the rowers sit in the boat the whole system moves as fast as the boat does. This simplistic observation leads to erroneous coaching theories, which can harm performance in rowing when it is advised to maximise handle-gate force in order to accelerate the boat and at the same time suggesting to minimise the force on the foot stretcher, because it pushes the boat backwards.

The following steps will help to understand the principles of effective rowing technique:
1. To increase the boat speed, rowers have to expend more power to overcome higher drag resistance (P = kv3).
2. The kinetic energy of the whole boat-rower system can be increased (accumulated) only during the drive phase. The increase of the shell's velocity during the recovery is explained by the transfer of the crew’s kinetic energy
3. Because the crew's mass is higher than that of the boat, the crew accumulates 5-6 times more kinetic energy than the boat (Ek = mv2/2). Therefore, the main target for an effective drive phase is to increase the velocity of the crew's centre of mass.
4. The only force accelerating the rower’s centre of mass forward is the reaction force on the stretcher. Therefore, maximizing of the stretcher force is the main target of the drive. The handle force pulls the rower backwards.
5. To apply a high stretcher force is not enough for a rower’s acceleration. The stretcher must have a supporting connection to the water through the rigger and oar.
6. The stretcher (and the whole shell) has to move fast forwards at the moment of the leg drive. Thus, rowing can be considered as a series of jumps where each drive phase is a jump and recovery is a flight phase. With this consideration longer jumps or higher jump frequency results in higher rowing speed. The major difference between rowing and real jumping is that rowers have to create support on the stretcher by placing the blade in the water and applying handle force.

Timing of the stroke cycle

Temporal or phase analysis plays an important role in modern sport biomechanics and is the most versatile biomechanical method of analysis across different sports. Other methods based on mechanical parameters (position, velocity, force, etc.) have very different nature in various sport motions. The phase analysis is based on time only and can represent different motions as a sequence of phases and sub-phases.

The accelerations of the boat, rowers’ and system centre of mass as well as the oar and seat velocity are used for definition of the micro-phases of the stroke cycle. Figure 10 shows biomechanical parameters of a single sculler obtained during detailed measurements.

Six micro-phases of the drive phase (D1-D6) and three micro-phases of the recovery (R1, R2, R3) are defined in Table 6.

Table 6. Micro-phases and key events of the stroke cycle.

No.

Key event description

Micro-phase ID

Micro-phase description

1

Catch, beginning of the drive. Oar changes direction of movement

D1. Blade Immersion

The system’s acceleration is still negative. Small inertial forces applied to the handle and the gate, but the foot-stretcher force is already significant. This produces a negative peak of the boat’s acceleration and a positive peak of the rower's centre of mass acceleration. Fast increase of handle and legs speed

2

The system’s acceleration becomes positive. The centre of the blade crosses the water level

D2. Initial rowers’ acceleration

Handle force increases, which leads to the gain of the boat’s acceleration, but it is still negative and lower than the rowers’ centre of mass acceleration.

3

The boat’s acceleration become higher than the rowers’ centre of mass acceleration. This is caused by the increase of the gate force, which becomes higher than the stretcher force

D3. Initial boat acceleration

First positive peak of the boat’s acceleration and cavity of the rower's acceleration. The blade is fully immersed. Maximal speed of the legs

4

The boat’s acceleration decrease and becomes lower than the rower’s acceleration. This is caused by the increase of the stretcher force, which again becomes higher than the gate force

D4. Rowers’ acceleration

Forces, the rower's and system accelerations increase slowly. Handle speed continues to grow. Legs speed decreases and trunk speed increases

5

The boat’s acceleration again becomes higher than the rowers’ center of mass acceleration. This is caused by a decrease in the foot-stretcher force, which becomes lower than the gate force

D5. Boat acceleration

All forces are decreasing, but the foot-stretcher force is decreasing faster than the gate force, which produces the highest boat acceleration. The rower's and system’s acceleration decrease. The oar crosses the perpendicular to the boat. The handle and trunk achieve their maximal speed.

6

The system’s acceleration becomes negative. The centre of the blade crosses the water level

D6. Blade removal

The handle continues to move towards the bow. The arms achieve the maximal speed. The rower's mass is begins the recovery phase (negative acceleration). Nearly zero boat acceleration

7

Release, end of the drive. The oar handle movement changes direction toward the stern

R1. Arms and trunk return

The moment of inertia transfers from upper rowers’ body to the boat mass. This causes a quick positive peak of boat acceleration and negative rower’s acceleration

8

The seat starts moving toward the stern. This causes an increase of the boat’s acceleration and a quicker decrease of the rowers’ center of mass acceleration

R2. Legs return

The boat acceleration is positive (depending on the stroke rate), but rower’s and system accelerations are negative. The legs speed towards the stern increasing. Arms are nearly strait, trunk crosses the vertical position

9

Rower starts pushing foot-stretcher. The speed of the seat decreases and the boat’s acceleration becomes negative

R3. Catch preparation

Rowers push the stretcher stronger. This causes the boat deceleration, but rowers’ centre of mass starts acceleration. Arms and oars prepare for the blade entry to the water.

 

Figure 9. Micro-phases of the stroke cycle (key event and the following phase). Men’s pair James Tomkins and Drew Ginn, Olympic Champions of Athens Games 2004. Stroke rate 36.5 str/min, video 25 fps, frame number – micro-phase.

 Figure 10. biomechanical parameters and micro-phases of the stroke cycle (M1x, rate 32 str/min). Key events are marked with circles.

During D1 – D2 the rowers push to accelerate their body mass and decelerate the boat, because they have to change direction of their movement from the stern to bow at catch. The quicker these micro-phases, the better. Then, during D3 the rowers accelerate the boat to create faster moving support on the foot-stretcher to further accelerate their bodies. This micro-phase is extremely important for performing effective drive phase but in some crews this phase can be absent. Fast increasing of the handle force is the main condition of its presence.

During D4 the rowers push the stretcher again to accelerate themselves and accumulate the main part of kinetic energy. Effectiveness of this phase depends on the amount of gained boat speed during the previous D3 and fast powerful legs drive. The final boat acceleration micro-phases D5 and D6 utilize more pull by means of trunk and arms work. Forces and total system acceleration decrease during this phase and rower’s acceleration become negative transferring kinetic energy to the boat. This push-pull-push-pull coordination during the drive requires coordination and “boat feel” from the rowers.

Biomechanical variables

Rowing provides an excellent model for biomechanical measurements. The first of such measurements were carried out by Atkinson in 1896. Since then, the biomechanical measurements have become common practice both for research and athlete training purposes in major rowing countries. The main variables of the rowing biomechanics are: the oar angle, force application, boat velocity and acceleration, and body segments movement.

Oar Angle

The horizontal oar angle defines the amplitude of the rower’s movement. The angle is measured from the perpendicular position of the oar relative to the boat axis, which defines zero degree. The catch angle is defined as the minimal negative angle and the release angle is the maximal positive angle. The horizontal oar angle is used for definition of the start of the stroke cycle, which occurs at the moment of zero oar angle during recovery (Kleshnev, 2005).

Table 7. Average oar angles in different categories of rowers at racing stroke rate

Categories

Catch angle

Release Angle (deg)

Total Angle (deg)

Men scull

-66.5

43.8

110.4

Men light scull

-64.5

42.6

107.1

Men sweep

-56.8

34.3

91.2

Men light sweep

-54.3

33.6

87.9

Women scull

-62.2

43.0

105.2

Women light scull

-61.3

42.8

104.2

Women sweep

-53.5

33.4

86.9

 

The total rowing angle can be 4% longer at the lower stroke rate 20-24 str/min. A vertical oar angle is useful for defining of the rower’s oar handling skills. It reads zero degree when the centre of the blade is at the water level and negative downwards.

Forces

The forces in rowing are usually measured at the handle and at the gate (pin).
The handle force can be determined by means of measuring the bend of oar shaft. The point of the handle force application is not certain, especially in sweep rowing, where the rower can pull more with the inside or the outside arm. This can create a problem if the ambitions is to know the handle force itself, but it produces more reliable values of rowing power applied to the handle, because it is calculated using the moment of force (Kleshnev, 2000).

The gate force is measured using specially developed instrumented gates. This method produces more accurate and informative data on the force applied to the boat, but calculation of the power from the gate force is not accurate.

Table 8. The handle forces and rowing power at racing rate in different categories of rowers

Rower’s categories

Maximal Handle Force (N)

Average force during the drive (N)

Rowing power (W)

Men scull

766

405

528

Men light scull

692

360

464

Men sweep

671

331

520

Men light sweep

590

294

425

Women scull

547

286

329

Women light scull

477

253

285

Women sweep

479

238

308


The graph of the force relative to time or horizontal oar angle called “force curve”, which is a valid indicator of rowing technique. Peak force develops earlier in big fast boats and at higher stroke rate.

Body segments input

On average, each of three body segments contributes approximately one third to the total length of the stroke arc (legs a bit more, trunk a bit less). The legs execute their work during the first half of the drive, when the force exertion is maximal. Therefore, the legs produce nearly half of the rowing power (46%); the trunk produces nearly one third (32%) and arms a bit more than one fifth (22%). As higher stroke rates the legs increase their percentage contribution power. Thus, trunk muscles utilize only about 55% of their work capacity during rowing. At the same time, the arms use about 75% and the legs up to 95% of their respective work capacity.

Rowing technique

Rowing styles and efficiency

Rowing styles are defined by movement of two biggest body segments: the legs and the trunk. The most popular attempt of classification of rowing styles was by Klavora (1977), which defines the following three main styles.

• The Rosenberg style is named after Allen Rosenberg, who was the head coach of many USA national rowing teams from 1961 to 1976. This is the most traditional style and inherits developments in technique introduced by the great English-Australian coach Steve Fairbairn in the end of 19th - early decades of the 20th century. This style is characterised by large forward declination of the trunk at the beginning of the stroke, then strong leg extension without significant trunk activation. At the end of the cycle the trunk stops in the deep backward position.
• The Adam style was developed in 1960-s by the innovative coach Carl Adam from West Germany. This style has a comparatively long leg drive, limited amplitude of the trunk and simultaneous activity of legs and trunk during the stroke.
• The DDR style was developed by coaches and scientists of East Germany – the most successful rowing nation in 1970-s. The style is characterised by large, forward declination of the trunk, which begins the drive, followed by simultaneous activity of the legs.

Two main factors, which distinguish these styles are timing (simultaneous or consequent activity of two biggest body segments) and emphasis during the drive (on legs or trunk). These factors can be illustrated as X and Y axes of a quadrant (Figure 11).

The three mentioned styles perfectly fit three quarters of the quadrant. However, a fourth rowing style exists. This style has consequent timing and emphasis on the legs drive. This style may be called the “Grinko style” after the talented Russian coach Igor Grinko who coached World Champions M4x of USSR and then 1990 World champion and 2004 Silver Olympic medalist in M1x Jueri Jaanson. This style inherits the traditions of the USSR school of rowing technique, which produced great rowers in 1950-60 including three times Olympic champion Viacheslev Ivanov.

 Figure 11. Quadrant of rowing styles

The rowing style correlates with the shape of force curve, which affects amount of power generated and blade propulsive efficiency. A sequenced work of the legs and trunk (Rosenberg and Grinko rowing styles) usually produces triangular shape of the force curve and higher peak force and power values (Figure 12). This leads to higher slippage of the blade through the water that causes energy losses. Lower blade propulsive efficiency, however, can be more than compensated for by higher values of force and power produced per kg of body weight. Active use of the trunk produces even more power and the Rosenberg style can be considered as the most powerful rowing style.

Simultaneous work of the legs and trunk (the two German rowing styles) produces more rectangular shape of the force curve, but the peak force and power are lower (Figure 12, b). More even pressure on the blade improves its propulsive efficiency. However, slower and more static character of the legs and trunk work does not allow delivering its optimal power.

Figure 12. Effect of the segments sequence and emphasis on the shape of power curve.

Emphasis of legs or trunks work affects position of the peak force and power. Styles with the legs emphasis (Adam and Grinko styles) allow quicker increase of the force and earlier peak of the force curve. This increases the initial boat acceleration micro-phase D3, improves the temporal structure of the drive and makes it more effective. Styles with the trunk emphasis (Rosenberg and DDR styles) produce more power because of better use of big muscle groups as the gluteus and longissimus muscles. However, these muscles are congenitally slow because they are intended to maintain body posture. This fact together with the significant mass of the torso do not allow for a quick increase of the force and shift the peak of the force curve closer to the middle of the drive, making the temporal structure of the drive less effective.

It is, however, uncommon that these rowing styles are found in their pure form. Most rowers adopt a hybrid style in-between these four extremes. The choice of style depends on many factors including body structure of the rowers. For example, it is unlikely that rowers with short legs will adopt a style that emphasises the importance of a long slide.

Coordination, coaching and feedback

Rowing looks quite simple, but in fact it requires very high coordination and sophisticated motor control. The rower has to coordinate his body movement along with the oar’s 3D movement and to maintain the balance of the boat. The task becomes even more complicated in crews, where each rower has to synchronise his movements with that of other members of the crew. Due to short time of the drive phase (<1 s) and the fast movement of big muscle groups, rowers can not change movement pattern during the drive. They can only evaluate their sensations after completion of each stroke and make corrections for the next one. The coach watches the crew and compares his visual impression with the an ideal model of the rowing technique. He then gives verbal feedback to the rowers, which can have more or less immediate nature: after each stroke, after completion of a bout of training, after a session, a day, or a week. A good coach also asks for feedback from the athletes that help him to evaluate the effectiveness of his actions and to find better methods of technique correction.

Several technical tools have become popular for giving feedback to rowers and coaches:
• StrokeCoach and SpeedCoach ™ provide immediate feedback on stroke rate and boat speed;
• Visual feedback can include videotape and replay after the session or in immediate mode using a personal head mounted display;
• Biomechanical data acquisition systems can measure the force applied by the rower, oar angles and other mechanical parameters (seat and trunk position, etc.).
This equipment looks attractive and are powerful tools for correction of rowing technique. However, it is necessary to understand what needs to be corrected and in what direction. Proper theory of rowing biomechanics is crucial when using technical methods of rowing technique correction.

References

1. Atkinson E. 1896. A rowing indicator. Natural Science. 8, 178.
2. Caplan, N. Gardner, T.N. 2005 A new measurement system for the determination of oar blade forces in rowing. In Proceedings of the 3rd IASTED International Conference on Biomechanics, (ed. Hamza, M.H.) Acta Press, Calgary, Canada
3. Concept 2 web site www.concept2.com/05/oars/vortex1.asp
4. Filter K., 2000. Effect of wind on boat speed. Materials of FISA coaches conference in Seville.
5. Klavora P. 1977. Three predominant styles: the Adam style; the DDR style; the Rosenberg style. Catch (Ottawa), 9, 13.
6. Kleshnev, V. 2000 Power in rowing. Proc. Of XVIII Congress of ISBS, Hong Kong, Vol.II, 662-666.
7. Kleshnev V. 2005. Technology for technique improvement. in: Nolte V. (ed.) Rowing Faster. Human Kinetics. 209-228.
8. Nolte V. 2005. Rigging. in: Nolte V. (ed.) Rowing Faster. Human Kinetics, 125-140
9. Sanderson B, Martindale W. 1986. Towards optimizing rowing technique. Med Sci Sports Exerc; 18 (4): 454-68 


Monday
Aug082011

Applying Biomechanics to Improve Rowing Performance

By: Peter Schwanitz (GER)
From: FISA Coaching Development Programme Course - Level III
Site Link: Remo2016
Article Link: Applying Biomechanics to Improve Rowing Performance

Translated from German by Lena Baden and Fred Kilgallin 


1. Improvement of Rowing Performance 

Every rowing race has a winner. This winner - the individual or the crew - has rowed the racing distance in the fastest time with the highest average boat speed. The final performances by rowers in the finals of the top international competitions (World Championships and Olympic Games) are the result of important and complex efforts by the rowers and the coaches.

The results make it possible to evaluate, among other things, the effectiveness of the training, the creatively efficient effort of the athlete during training and competition, and the development of modern materials for the production of boats, oars and other equipment. In order to draw conclusions about future success in competitive rowing, it is important to have a general idea of the trends in racing times in the finals of previous top international competitions. If this is regarded as a benchmark for the development of performance requirements in rowing, it is important to emphasise that performance is influenced by two factors: The human factors (personal abilities, fitness, rowing technique, etc.) and the non-human factors (boat equipment, weather, regatta course, etc.).

Three questions about the development of performance will be addressed in this section. The answers to these questions are based on the following:
• the winning times of all boat classes for men in the World Championships and the Olympic Games; and
• the results of test races performed in measuring boats by FES-Berlin in co-operation with Humboldt University in Berlin. 

Question 1: How has race performance (boat speed, racing times) developed?

Figure 1 shows the development of the boat speed of winners of the Olympic finals in all men's boat classes (average) from 1948 to 1988. 

If you analyse the average boat speed of all winners of the men's Olympic finals (except the 4x) from 1948 (London) to 1988 (Seoul), it is clear that from one Olympic Games to the next, the average boat speed over the racing distance has increased by 1.3 percent.

It is interesting that the development in the average first-place time corresponds to the relative development in the single sculls. From this one can cautiously draw conclusions about the development of the individual performance.

Figure 1: Development of the boat speed of winners of the Olympic finals in all boat classes (average) from 1948 to 1988. 

If this period of time is divided, then (see dotted lines in Figure 1) from 1948 (London) to 1968 (Mexico) the first-place time in an Olympic cycle improved by an average of 0.4 percent; while from 1968 to 1988 (Seoul) the first-place time in an Olympic cycle improved on average 1.9 percent. Winning times in the period since 1968 have improved at a rate greater than the previous period.

The result is that boat velocity, as a mean value for Olympic winners of all boat classes, has increased on average by 1.9 percent in an Olympic cycle. The relationships in velocity between boat classes (mean values) of the winners have stabilised (see Table 1). 

Table 1: Speed relationships for men (winners in all World Championships and Olympic Games 1958-1989) as a percentage of the men's eight.

Question 2: How are the racing performances in the Olympic cycles of 1992 and 1996 likely to develop?

Future increases in speed over 2,000 meters have been calculated based on improvements in performances. It should be noted that weather is included as an "average condition." Therefore, the expected improvements imply "average" weather conditions (i.e., calm, small waves, etc.). For example, for the three boat classes, 1x, 2- and 8+, the improvement in the racing times and the boat speed in the cycles of 1992 and 1996 are clear in Table 2.

Table 2: Mathematical adjustment of the improvement in boat speed from the World Championships and Olympic Games, 1974 to 1988, (winning performance) and concluding in 1992 and 1996. 

Question 3: How are the key technical parameters likely to change in the cycles of 1992 and 1996?

Assuming a constant stroke rate in the three selected boat classes, the Olympic winner in 1992 and 1996 will have to:
• reduce the total number of strokes in a race;
• increase the propulsion per stroke in comparison to the winners of 1988 and 1992 (see Tables 3 and 4).

Table 3: Increase in propulsion (cm) per stroke and reduction in the number of strokes (SZ) as a function of reduced racing times and constant stroke rate (1988, 1992, 1996). 

Table 4: Increase in the stroke rate as a function of reduced racing times and constant propulsion per stroke. 

Now it is interesting to see the consequences of the probable quantitative improvement of important rowing technique parameters and their relative percentage changes (see Table 5). These data were obtained from measurements of the former East German National Team.

Table 5: Empirical, mathematically based consequences of the improvement in boat speeds from 1974 to 1988 for the quantitative shaping of biomechanical parameters in a representative rowing cycle (X), (parameter as [power-] function of the boat speed).

PIHZ = power in the full rowing stroke, PIHEF = power in the effective drive portion, FIHEF = force on the inboard or inside lever, and VIHEF = velocity of the inboard or inside lever. P = mechanical performance, F = force, V = velocity, IH = inboard, and EF = effective drive ("work in the water").

In the three boat classes the highest percentage rates of increase in the realised average performance (P) on the inboard (PIH) are shown for:
• a rowing cycle (PIHZ);
• the effective drive (PIHEF) in the rowing cycle.

The product of the factors "force on the inboard or inside lever" (FIHEF) and "velocity of the inboard or inside lever" (VIHEF) with the mechanical performance of the inboard show a minor rate of increase within an Olympic cycle.

In general it should be noted that the increase in boat speed puts demands on the athlete to exert more power on the inboard and to attain a higher velocity on the inboard. 

2. Applying Interdisciplinary Contributions to Improve Performance

The definition of biomechanics can be described as the effects of mechanical laws on and in the living organism and the mechanically measurable reactions of the organism to these effects.

Thus, biomechanics has its basis in both the physical and biological sciences. Therefore, one should not depend solely on mechanical findings to determine how to achieve competitive goals (victory, best possible result, "faster," etc.).

This knowledge must be translated for use in an interdisciplinary synthesis and an application oriented training plan. The following four questions and their answers attempt to substantiate this claim.

Question 1: What are the possibilities and limitations of the contributions of biomechanics to the sport of rowing?

The essential focus of biomechanics in rowing has and always will be rowing technique.
Most objectives of biomechanical research are to explain the propulsion-causing powers and accelerations of the rowing stroke during competition, both in theory and in practice. This research also tries to explain the effects of the development of equipment.

Theoretically explained biomechanical knowledge and the empirical findings that create successful rowers are the bases for forming a technical concept. The application of this concept has contributed to the improvement of rowing performance.

The biomechanics of athletic movements in the endurance sport of rowing can improve performance, especially if it considers biomechanical/energetic and biological/energetic interactions. The task in this connection is:
• to investigate the movement sequences during competition and training in order to explain those mechanical causes that influence the biological/conditional effects;
• to develop rowing technique as a biomechanical solution process that can be applied to the effective biological/energetic development in training as well as result in higher speed during races.
It is important to develop and identify rowing technique from a biomechanical perspective, which makes it possible for the athlete:
• to achieve the fastest racing times and the highest average boat speed over the rowing distance on the basis of his or her individually available energy potentials at the lowest possible external resistance;
• to achieve the fastest time over a given distance on the basis of his or her individually available biological energy potential and taking into account the biological/conditional objectives for the particular training areas at given resistance conditions (boat type, gearing, area of blade, etc.). 

Question 2: What research could form the basis for the establishment of a rowing technique for training and competition?

In practice you can find different force/time-curves on the oarlock [F=f(t)] with an approximately equal impulse area. These can be classified as shown in Figure 2.

"A" emphasises the middle of the drive: Synchronous force of leg, upper body and arm musculature is dominant. "B" emphasises the end of the drive: Synchronous force of upper body and arms musculature is dominant. "C" emphasises the beginning of the drive: Synchronous force of leg and upper body musculature is dominant. "D" strongly emphasises the beginning of the drive with no emphasis on the remainder of the drive.

Figure 2: Schematic representation of different force/time-curves in rowing.

 

 

Figure 3: Schematic representation of typical curves as a function of distance with constant work (acc. Müller, 1962).

 

 

The strongly schematicised force/time-curves appear in rowers of all classes, including World and Olympic champions!

But which of these curves will now be useful? Trying to get the answer from the science of biomechanics alone wouldn't be enough. The following accounts should give some help in making decisions.

"The work is all the more inefficient the more tension there is in the muscles at the end of the effort, because the work is wasted isometrically, without producing any performance." (Landois-Rosemann 1962, p. 504)

"The force/distance-curves with a short steep rise to the peak of maximum force and a subsequent flatter fall off to the end of the work distance appears to be the most favourable. The effectiveness of the energy turnover for equal work is, in comparison to other curves, the highest, since the necessary energy turnover is the lowest." (Landois-Rosemann, 1962)

This information disqualifies an orientation toward hard pressure at the finish of the rowing stroke, and it highlights an emphasis on the beginning of the stroke.

"Equal work, realised through extreme tension of the different muscle groups, results in various local loads. The higher loads manifest themselves in the smaller muscle groups (i.e., the arms), and the lower loads in the larger muscle groups (i.e., the legs)." (Hollmann/Hettinger, 1976)
From this statement it makes sense to employ a synchronous whole-body effort of muscle potentials, taking into account the different force potentials of the leg, back and arm muscles. Emphasis on the finish of the stroke should be de-emphasised because of the high local load on the arm muscles.

"There are two alternative ways to increase performance (in the mechanical sense, as a product of force and movement velocity): you can increase either the force or the movement velocity. The physiological processes react more strongly to changes of movement velocity than to changes in force." (Landois-Rosemann, 1962; Roth/Schwanitz/Körner, 1989)

Thus, it makes more sense to improve the time of the movements during the drive where the body parts work synchronously. The necessary high velocity on the inboard can be carried out through the slower movements of the legs, upper body and arms while they work individually.

"A high force development in the beginning of the stroke seems to be the most effective with regard to the most favourable body position for a proportional development of the force potentials. The position of the body in the beginning of the drive can be compared to the position of a weightlifter at the beginning of the lifting process." (Gjessing, 1979)

In light of the previous statement, one should emphasise the beginning of the drive portion of the stroke. Empirical research carried out by this author has produced the following results:
• The average boat speed per stroke rose with the rower's increased force exertion on the inboard at the beginning of the drive.
• The increase in boat speed did not parallel the increase of average force past the 90-degree position of the oar relative to the splashboard.
• The recorded increase of inboard velocity in the area of the drive is therefore mostly a function of higher boat speed initiated by the higher inboard force at the beginning of the drive. (Schwanitz, 1975)

Therefore, one can justify an emphasis on the beginning of the drive as well as an orientation toward increasing the force in the middle of the drive and in the finish in order to make use of reserves. (Schwanitz 1976) In the discussion about the effectiveness of the rowing stroke, Nolte (1985) raised the aspect of the hydrodynamic lift, which supports the orientation toward the beginning of the drive.

3. Summary

From a biomechanical, biological and training method point of view, there are reasons for an efficient rowing technique that take into account the aspect of load as well as the propulsive effect during training and competition. The emphasis of the force on the inboard, in order to produce a powerful first part of the drive, characterises this rowing technique and should be encouraged.

In addition to the emphasis on the first part of the drive, the force on the inboard should be produced in the tangential direction to the inboard, especially before the 90-degree position. A common expression for this force application would be "row around the oarlock."

The intention of all training methods is to increase the individual performances in the drive phase. This also covers the common forms of diagnosis used in biomechanics, rowing technique and sports medicine. These usually show the effects of training under defined test conditions.

The increased force exertion and movement velocity as components of the mechanical performance are the correlated partners of the biological and mechanical criteria, with the drive given first priority. Here one should pay attention to the fact that the co-ordination requirements of the recovery phase are particularly high. In training it is important to carry out a conscious conditioning of the muscles used during the recovery at race intensity to counter conditionally caused co-ordination problems and to ensure the propulsive effect in the drive by paying special attention to the reversal movement into the entry.

Question 3: What should the coach and athlete know about rowing in different boat classes?

An analysis of training methods with the boat measurement technology of FES Berlin in 1978 gave results which, later, strengthened the considerations of the rowing federation of the former GDR with regards to decisions about loads. Rowing in different boat types will, under the same training conditions (distance, stroke rate), put different demands on the athlete and result in different loads. A comparative examination of inboard velocities in similar training load ranges gives the following results:
• Recovery: The profile of the inboard velocity and the time bases approximately match in the various boat classes.
• Drive: As the boat classes get bigger the acceleration on the inboard in the beginning of the stroke increases, and the drive time decreases considerably. (Refer to Table 6)

Table 6: Load relevant to aspects of changes in the mechanical work in rowing.

Then, in the direction of the ARROW:
• the amount of inboard power during the drive-phase decreases
• the inboard velocity during the drive-phase increases
• the time of the recovery increases

Question 4: How does the individual rower deal with the requirements of the specific boat classes?

The research in the biomechanically explained movements of the different boat classes made it possible to qualify the diagnostics of the measurement boats in such a way that the individual load requirements and effects during training could be clarified, along with the development of rowing technique. This led to an experiment in 1987 carried out by Körner (training methodology), Roth (performance physiology) and Schwanitz (biomechanics).

The object of the experiment was the rower's mastery of the boat type specific requirements. Four athletes each carried out the following tests in 1x, 2+ and 4+ measuring boats:
• a five-step test (one step: three min.);
• one unit of basic endurance training (90 min.; stroke rate = 20 to 22).

Inevitably, there were the same general requirements (stroke rate, boat velocity) for every step for the four rowers in 4+. However, every rower showed very different realisations of the demands of every load level from the biomechanical point of view. The analysis of the biomechanical parameters shows great dispersion among the rowers at the same load input (between 4 and 25 percent). It was striking that:
• the highest individual deviation in the load steps appeared at lower intensity;
• at all load levels the inboard velocity showed the smallest individual deviation, which is mechanically explainable.

The overall impression of a team is often formed by that which one can see, such as movements of the body parts relative to each other and to the boat as well as movements of the oars and the boat. In general, one can conclude that:
• The different load demands of each boat class and of each step in the test show very individual results in rowing technique and physiological load;

• In every load of the step test the performance on the inboard as the product of the inboard force and velocity shows particularly large differences for every rower in all boat classes;
• Performance, force, velocity, lactate and other biological parameters determined as a function of the load in the different boat classes by the same rowers confirm the necessity and the possibility of emphasising the individual control of performance development by means of biomechanical/rowing technique parameters and characteristics. (See an example of this analysis in Figure 4.)

Figure 4: Lactate as a function of the power of rowers of a 4+ in a measuring boat.

The results of this experiment were used to prepare the athletes of the rowing federation of the former GDR for the 1988 Olympic Games in Seoul. Early in 1988 the women's sweep rowing team was diagnosed according to this method and given training recommendations. Later in June selection tests were carried out to form the crews in the different boat types.

A basic-endurance load test of more than 90 minutes at the stroke rate 20 to 22 showed:
• large differences among rowers in performance, force and velocity on the inboard;
• different amounts of force and velocity among the rowers;
• different lactate concentrations that prevented at least one rower from reaching the biological/conditional training goal.

As the training progressed all four athletes tended to:
• decrease the inboard velocity during the drive;
• increase the inboard velocity during the recovery;
• reduce the force on the inboard;
• reduce the performance on the inboard during the drive.

The following facts can be applied to the examined boat classes:
• Depending on the length of time and intensity of the training session on the water, a relatively early tendency of decreased rowing technique was observed;
• The biggest deviations in the technical parameters from rower to rower happened under low intensity training.

These facts strongly support Roth's demands in 1987 for a transition from a methodology/biological training concept to a methodology/biomechanical training concept to improve the performance of the active rowers.

4. Conclusion

The previous improvements in the times and the average boat speed in the finals in top international competition are milestones in the development of rowing performances. They are the results of human factors, developed by training and experience, and influenced by non-human factors. In terms of Olympic cycles, the relative increases in the average boat speed of 1.5 percent to 2.0 percent are also likely in the future.

The biomechanics of athletic movements based on physical and biological sciences can improve rowing performance, especially in biomechanical/energetic and biological/energetic contexts.

The following two essential tasks should be emphasised:
• the improvement of rowing technique to help the biological/energetic development during training, which leads to a higher boat speed and faster times in competition;
• the examination of movement patterns during competition and training to explain the mechanical causes in biological/conditional effects.

From a biomechanical and biological point, there are reasons for adopting an efficient rowing technique, the most important characteristic of which is the emphasis on the first part of the drive.

In order to perfect the technique and fitness as a synthesis for further improvement in rowing performance, one should find and pay special attention to the specific aspects of each boat class and the individual use of these characteristics.

The conscious use of the boat characteristics depends on one's knowledge of rowing in big boats versus small boats. For example, when going from a small boat to a big boat, one experiences:
• reduced drive times;
• increased inboard velocity;
• increased emphasis on the first part of the drive;
• reduced drive phase proportion in comparison to the whole stroke cycle (changed rhythm relations);
• increased inboard velocity in the performance of the drive.

Knowing about the individual characteristics of a certain boat class, one will be able to prescribe the correct workload, and gear the athlete in training toward a successful performance.

Diagnostic methods to check certain abilities specific to rowing should allow a variation of the loads that will enable the athlete to reach the limits of his or her current individual ability. It is therefore possible to make low risk assessments of the training effectiveness, and to give recommendations more likely to succeed in the further development of performance.

A diagnosis of the rowing technique should be done along with keeping track of the rowing performance. For this reason it is recommended that you make a system of diagnoses (video analysis, dynamic-graphical measurements, individually or together):
• full stroke cycle and drive portion evaluations;
• competitive evaluations in test and regatta environments;
• workload evaluations.

Abbreviations

Variables:
P = Performance
F = Force
V = Velocity
T = Time
S = Distance
Indices:
B = Boat
EF = Effective Drive
IH = Inboard part of the oar
FL = Recovery
Z = Rowing Cycle

Example:

PIHZ = average performance (P) on the inboard (IH) of one rowing cycle (Z) in the rowing stroke.
Reference parameters:
SF = Stroke Rate
GA = Basic Endurance
WSA = Specific Endurance necessary for Competition
S = Sprint
WK = Competition

References

1. Andrich, B., R. Buchmann, P. Schwanitz: Ansätze für die Erarbeitung biomechanischer Zweckmässigkeitskriterien sportlicher Bewegungshandlungen in Ausdauersportarten fur Wettkampf und Training. In: Theorie und Praxis der Korperkultur 38 (1989) 6, p. 420-422.
2. Gjessing, E.: Muskeltätigkeit und Bewegungs verlauf beim Rudern -eine Kraftanalyse. In: FISA Coaches Conference, 1976, p. 15-35.
3. Hollmann, W., T. Hettinger: Sportsmedizin - Arbeits - und Trainings-grundlage. Stuttgart, 1980.
4. Müller entnomment Landois-Rosemann: Lehrbuch der Physiologie des Menschen. Vol. 11, München - Berlin, 1962, p. 504
5. Nolte, V.: Die Effektivität des Ruderschlages. Berlin, 1985.
6. Roth, R., P. Schwanitz, T. Körner: Untersuchungen zum Freiwasser-Mehrstufentest in den Messbooten Vierer, Zweier, Einer in fünf Geschwindigkeitsstufen. DRSV-intern, Berlin, 1989.
7. Schwanitz, P.: Ruderspezifische Systembetrachtung und Analyse der Veränderungen Rudertechnischer Parameter in drei Geschwindigkeitsstufen. Dissertation, Humboldt-Universität in Berlin, 1976.