Early Bird Swimmers Do Not Get the Worm

The findings of a circadian biologist.

March 2021

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Early Bird Swimmers Do Not Get the Worm

Illustration: Michele McCammon

Olympic swimmers are faster in the evening. Specifically, at 5 p.m. Circadian biologist Renske Lok, a postdoctoral fellow in psychiatry and behavioral sciences, analyzed the race times of swimmers from the past four Olympic Games and found that evening times were about .39 second speedier than morning times. For those playing along at home, that’s about the amount of time it takes you to blink your eyes; but for world-class swimmers, it’s enough time to grab coffee and a bagel. An elite athlete could harness these findings to modify her sleep habits: Nudging her circadian rhythm by waking earlier or later to adapt to the hour of the upcoming competition might make the difference between silver and gold. For those of you whose athletic aspirations tend more toward summiting the sofa, feel free to use this as an excuse to sleep in before a Netflix marathon. You want to be at your peak.

Summer Moore Batte, ’99, is the editor of Email her at

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