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The Science of Performance |
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How Different Are Elites?
In the 3 part series "How Much Can You Improve" we explored the wide variance in genetic talent in humans. Research revealed that the range of response to a standardized 3 days-per-week easy to moderate aerobic training program ranged from -5% to 56%. Other studies on this topic have confirmed the wide variance in response to training. Additionally, a study on identical twins revealed that genetics account for 75-80% of the variance in response to training. Though these studies clearly demonstrate the wide variance in response in training in humans they all used sedentary subjects. What these studies did not directly measure were the differences between elite subjects and sedentary ones. Are there measurable differences between untrained muscles in elite runners and non-runners? Readers familiar with Power Running know that I suggest that muscles, and not the aerobic system, are the primary determinants of endurance performance - i.e. muscles, and not the aerobic system, determine just how fast and far you can run. Further, I suggest that there are inborn (genetic) differences in the muscles of elite runners that allow them to perform as they do. If this is true, it is likely that these differences can be measured - that untrained muscles of elite runners will be measurably different than the same muscles in untrained subjects. This topic has been studied by researchers in an effort to determine if differences in performance between elites and average runners have a genetic component. Let's take a look at a research study designed to investigate this topic. Research Researchers wanted to investigate "whether genetically determined properties of muscle metabolism contribute to the exceptional physical endurance of world-class distance runners."(1) They recruited 4 world-class long distance runners to participate in the study. One of these elite runners was a recent world champion in the 1500m race, another was an Olympic alternate for the US in the marathon, and the other 2 were close to these in performance. 5 sedentary, healthy individuals were recruited as controls. In order to test for genetic differences in the muscles between the two groups required the researchers to test untrained muscles. Wrist flexor muscles (forearm muscles used for flexing the wrist) were selected because these muscles were untrained in both groups. None of the subjects engaged in any regular exercises that trained their wrist flexor muscles. Subjects were tested for the maximum voluntary contraction (MVC) strength of their wrist flexor muscles by depressing an exercise bar using just the wrist flexor muscles. After MVC was established subjects underwent exercise testing consisting of 2 cycles of 18 minutes of exercise per cycle. Each cycle consisted of depressing the exercise bar once every 5 seconds in 6 minutes intervals. Interval one (minutes 1-6) was conducted at 20% MVC, interval two (minutes 7-12) was conducted at 40% MVC, interval three (minutes 13-18) was conducted at 60% MVC, with no rest between any of the intervals. Upon completion of the the first cycle of exercise (minutes 1-18), subjects immediately began a second 18 minute cycle (minutes 19-36) of 20%, 40%, & 60% MVC, for a total exercise time of 36 minutes. Researchers used magnetic resonance spectroscopy to measure changes in various metabolites, including Pi, PCR, and ATP before, during, and after the exercise testing and muscle pH was estimated from the changes in these metabolites. Results Contractile Force: The elite runners were able to maintain the highest level of contractile force (60% MVC) in both exercise cycles without difficulty. In contrast, the control subjects were able to maintain 60% MVC with some difficulty in the first exercise cycle and in the second exercise cycle half of the control subjects were unable to reach the 60% MVC level.
Concentration of Metabolites: Significant differences in the concentration of various metabolites were measured between the elites and the controls. These differences consisted of either a higher initial level and/or a significantly faster return to baseline levels in the elites than in the control subjects. For example, the concentration of PCr in the resting untrained muscles of the elite runners was 25% higher than in the control subjects. The concentration of PCr remained higher in the elites throughout the testing period. Further, when the exercise resistance was reduced from 60% MVC at the end of the first exercise cyle to 20% MVC at the start of the second exercise cycle, PCr levels increased twice as fast in the elites as in the controls.
Additionally, pH in the elite athletes changed very little during exercise, decreasing no more than 0.1 pH units at any time during exercise. The control subjects decreased significantly (0.35 unit decrease) during the first exercise cycle, followed by a sharp increase by about 0.2 units at the start of the second exercise cycle. Discussion What do all these differences between the untrained muscles of the elites and control subjects tell us? They tell us that there are inborn differences in the muscles of elites and average subjects. Since untrained muscles were tested the measured differences are most likely due to inborn differences rather than training or lifestyle difference. None of the subjects - elites or controls - performed any exercise program that trained the flexor muscles of the wrist.. In accordance with prevailing thought on this topic, the researchers concentrated their examination on differences in muscle metabolism. Not surprisingly, the researchers attributed the differences in muscle strength and exercise capability to differences in aerobic factors. They suggested that "a superior oxidative capacity for energy production" explained the differences in performance observed between the two groups and also noted that these differences are "an important genetic attribute". The researchers did not examine other possible explanations for the differences in performance between the elites and the control subjects. Another possible explanation, one not addressed by these scientists, is that there are significant differences in muscle contractility between the elites and the controls. If this theory is correct, then the superior muscle contractility of the elites is supported by higher energy production by both aerobic and anaerobic energy systems - i.e. the higher aerobic capacity noted by the researchers in the elites is a by-product of superior contractility of the muscles and not the cause of their superior performance. Whichever explanation for the superior performance of the elites observed in this study is correct, it doesn't change the major finding of this study. Namely, the untrained muscles of elites are able to initially reach and maintain a high work load than non-elites and then to recover nearly twice as fast as non-elites. This indicates a strong genetic capability for endurance exercise and performance in the elite runners, a capacity much higher than that demonstrated by the controls. Finally, though the tested muscles were untrained, the possibility that the training of the elites had an effect on the untrained muscles can not be completely dismissed. However, this seems to be a remote possibility, one addressed by the researchers.
Summary A study of the untrained wrist flexor muscles of elite runners and controls reveals that the muscles of the elites are able to achieve and maintain higher work load than that achieved by average subjects. Additionally, the muscles of the elites recovered twice as fast as those of the control subjects. Since untrained muscles were tested, the large differences between the two groups indicate that elites are born with a significant genetic endowment for endurance exercise and performance. References: 1. Park J, Brown R, Park C, Cohn M, Chance B., Energy metabolism of the untrained muscle of elite runners as observed by 31P magnetic resonance spectroscopy: Evidence suggesting a genetic endowment for endurance exercise Proc. Natl. Acad. Sci USA Dec 1988, 85, 8780-8784
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