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Body's power supply impacts human speed recordsNEW YORK, Mar 16 (Reuters Health) -- Two 'power laws' seem to govern the record-breaking performances of world-class runners and swimmers, according to researchers who studied speed among the last century's world-record holders. The laws that govern racing speeds stem from when the body switches over from anaerobic (without oxygen) energy sources to aerobic (in the presence of oxygen) burning of fuel. What's surprising is that these laws are universal, applying to men and women of all ages and national origins, Sandra Savaglio told Reuters Health. Savaglio, a researcher at the Space Telescope Science Institute in Baltimore, Maryland, and colleague Vincenzo Carbone report their findings in the March 16th issue of the journal Nature. On the track and in the pool, human performance shifts abruptly once a certain distance is reached -- 1,000 meters in running and 200 meters in swimming, according to Savaglio and Carbone. They found that in events shorter than these thresholds, world-record speeds decline sharply as distance increases. But in running events longer than 1,000 meters and swimming races longer than 200 meters, the average-speed decline with increasing distance is not as dramatic. Instead, it looks more like a gentle slope. The two power laws seem to diverge at the point when athletes move from anaerobic to aerobic activity, Savaglio noted. During an exercise such as a sprint, athletes rely on short, powerful bursts of energy that come from anaerobic sources, readily accessed, but also quickly used up. Endurance races, however, are an aerobic activity, and athletes must burn oxygen and energy efficiently over the entire race. It is easier, in other words, to maintain a steady speed during a marathon than during a sprint. Across swimming world records, the speed decline in shorter races was not as sharp as that for running, but it followed the same pattern. Short swimming races, the researchers note, burn less oxygen than sprints do. The two power laws were constant across men's and women's races -- an interesting finding, Savaglio said, because it is widely believed that women are better endurance athletes than men. Women may, however, still have the upper hand in super-long endurance. This study looked at world records up to marathon distance only -- Savaglio said other research suggests that among the few athletes who race up to 60 miles, women burn energy more efficiently. SOURCE: Nature 2000;404:244.
Copyright 1999 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. |
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