Magazine article Science News

Endurance Superstars May Be 'Born to Run.'

Magazine article Science News

Endurance Superstars May Be 'Born to Run.'

Article excerpt

Endurance superstars may be 'born to run'

A study of muscle chemistry in world-class long-distance runners suggests these athletes' ability to "reach levels of physical endurance unattainable by all but a very few persons" lies largely in their genes, researchers report in the December PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (Vol. 85, No. 23).

Scientists have known that different people have different proportions of endurance, or "slow-twitch," muscle fibers relative to "fast-twitch," short-energy-burst fibers. They have also documented that training can alter the proportion of these two types. They have debated, however, how large a role genes play, says study leader Jane H. Park of Vanderbilt University in Nashville, Tenn.

"I think this is one of the first times people have said that genes are important [in determining human endurance performance]," Park told SCIENCE NEWS. One research team had suggested a genetic component when it found an "unexpectedly high" number of slow-twitch fibers in the untrained muscle of certain endurance athletes. However, "there are no earlier measurements of metabolites in untrained muscle of athletes to our knowledge," Park and her colleagues write.

They found that the untrained wrist muscles of the four long-distance runners studied maintained force better during prolonged exercise -- involving repeated wrist flexion against a resisting bar -- than did those of five healthy but relatively sedentary sex-matched individuals of comparable age. By measuring muscle metabolites -- chemicals involved in muscle contraction -- the researchers determined that the athletes' muscles sustained their chemical energy reserves much better than did those of the non-athletes. And indicators of muscle acidity showed that the athletes, unlike the controls, did not supplement their energy supplies through anaerobic muscle metabolism, which causes muscle fatigue and lactic acid buildup, according to Park. …

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