NEW 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.
