Sleep cycles can affect an athlete's performance

Science Friday
Emily Defroand (left) and Holly Payne (right), two University of Birmingham students who participated in a study that examined natural sleep rhythms and peak athletic performance.

Andy Smith

The number of factors that influence the outcome of a single game, such as this week’s Super Bowl, are too numerous to list. But a new study says that one factor can predict an individual athlete’s performance surprisingly well: that person’s sleep schedule.

The study, in Current Biology, finds that an athlete's peak performance can vary depending on natural circadian rhythms and what time of day his or her performance is measured.

Roland Brandstaetter, senior lecturer in the biosciences department at the University of Birmingham in Birmingham, England and co-author of the paper, measured a group of 20 athletes’ peak performance. He found that an athlete’s peak performance can vary as much as 26 percent, depending on what time of day the athlete competes and how in sync that time is with his natural body clock.

"If a 1 percent difference in performance can make the difference between 1st place and 4th place in a 100-meter race and actually win you the gold medal at the Olympics, then imagine what a 26 percent difference in your performance could give you," said Brandstaetter in a news release. "Our research takes us away from the idea of 'time of day of the race' and directs us more to internal biological time."

Researchers have long known that an individual’s natural circadian rhythm controls important physical and mental functions, including heart rate, body temperature, concentrations and reaction time, so it makes intuitive sense that it would also affect athletic performance. Now Brandstaetter may have the data to confirm it.

In the study, Brandstaetter categorized athletes as either "early morning larks" or "night owls" by measuring their circadian phenotype. “Larks” normally get up at around 7 o'clock in the morning and go to sleep around 11 pm, at the latest. The “owls”, if you let them, will get out of bed at 10 or 11 and then not go to bed before about 1 or 2 am, he says.

Brandstaetter conducted performance tests six different times a day between 7am in the morning and 10pm in the evening. The early types, the larks, showed their maximum performance around midday, while the owls showed their best performance around 8 o'clock in the evening. “And the intermediates really are intermediate,” Brandstaetter notes. “They show their best performance around 4 o'clock in the afternoon.”

The researchers found they could predict how well each group performed at a given hour based on elapsed time since their ‘entrained awakening,’ — that is, the time since they would have naturally woken up in the morning without any external prompting.

The findings "leave no doubt,” Brandstaetter and his team conclude, “that the correct determination of an athlete's personal best performance requires consideration of circadian phenotype, performance evaluation at different times of day, and analysis of performance as a function of time since entrained awakening.”

This knowledge could not only have important implications for individual athletes, but could also be useful in team sports. Knowing the proportion of larks and owls on a given team could, theoretically, provide that team with a competitive advantage, Brandstaetter says.

“If you have a squad of 20 people and let's say 12 of them are larks and you're playing at 10 in the evening, then you can be sure that you have an impaired team performance, because most of them are going to be tired,” he says. “So I think it plays a very big role.”mmm

This story is based on an interview that aired on PRI's Science Friday with Ira Flatow

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