Alex Hutchinson draws on the latest research to answer your fitness and workout questions in this biweekly column on the science of sport.
Am I better off getting up an hour early to work out, or sleeping for an extra hour?
Needless to say, your best bet is to get both the exercise and the sleep. That's certainly the advice that Charles Samuels, medical director of the Centre for Sleep and Human Performance in Calgary, gives to the Olympic athletes he works with.
Back in the real world, though, that's not always practical.
"It's average athletes who are the most likely to curtail their sleep to train," Dr. Samuels says. "They're getting up at 4 a.m. to run for an hour so they can get to work by 7 a.m."
But that's not necessarily a winning strategy, especially for people who are already operating on the least sleep they can handle. Incurring a steadily mounting sleep debt has well-known effects on mood and cognitive ability, and a few studies suggest that sleep also has direct links with physical performance.
Stanford University sleep researcher Cheri Mah presented preliminary results in June from a small study of five Stanford swimmers who increased their sleep time to 10 hours a night from their typical six to nine hours. The swimmers improved their reaction time off the start by 0.15 seconds, and similarly improved their turn time, 15-metre sprint time and kick rate.
For top athletes, getting enough sleep has long been considered the sort of bland good advice - like eating lots of vegetables - that is obvious but easy to ignore. Ms. Mah's continuing study (she reported last year that increased sleep improved the sprint time and the free throw percentage of Stanford basketball players) is far from definitive, but it represents a first step in the attempt to put this advice on more solid scientific footing.
Earlier this year, Dr. Samuels reported the results of two pilot studies with athletes from the national bobsleigh and skeleton teams and students at the National Sport School in Calgary in the journal Neurologic Clinics. Poor sleep quality was prevalent even in elite athletes, he found.
Dr. Samuels's research program also includes a project with the Canadian downhill ski team to investigate the link between inadequate sleep and injuries, as well as studies of how globe-trotting athletes can best adjust to crossing time zones.
For now, much of the advice Dr. Samuels can offer athletes is drawn from studies with other populations, such as police officers adapting to shift work, since research on sleep and sport remains in its infancy. One key conclusion is that there is significant variation among individuals, both in the amount of sleep needed and in the reaction to sleep deprivation. That means it is hard to pin down exactly when an hour of sleep is more valuable than an hour of exercise.
But if you already feel short on sleep, you definitely shouldn't short-change yourself further.
"In terms of overall training benefit, it's better to get your sleep, because the platform of good training is recovery," Dr. Samuels says.
Applying that advice doesn't have to be as onerous as it sounds.
"I know it sounds ridiculous to get 10 hours of sleep a night," Ms. Mah admits. "That's an extreme."
For the typical person, she says, consistently increasing the amount of nightly sleep by even a small amount can produce positive effects. And, as her study shows, even a few weeks of concerted sleep catch-up can have a measurable effect of performance - something to keep in mind before the next big game or race.
Alex Hutchinson is a former member of Canada's long-distance running team and has a PhD in physics.
Sleep tips for athletes
Make sleep a part of your regular training regimen.
Extend nightly sleep for several weeks to reduce your sleep debt before competition.
Maintain low sleep debt by getting a sufficient amount of nightly sleep (seven to eight hours for adults, nine or more hours for teens and young adults).
Go to bed and wake up at the same times every day.
Take brief naps to obtain additional sleep during the day, especially if drowsy.
Source: Cheri Mah, Stanford Sleep Disorders Clinic and Research Laboratory
Exercise as sedative
Just as sleep helps exercise, the converse is also true. A new study from the Federal University of Sao Paulo found that moderate aerobic exercise (but not strength training or heavy aerobic exercise) increased reported sleep time 37 per cent in a group of chronic insomniacs.
One caveat is that exercise in the three hours before bedtime may hinder sleep in adults in their 30s or older if they already struggle with sleep, notes Calgary sleep researcher Dr. Charles Samuels, who was not involved in the study. "If you're a good sleeper," he adds, "nothing matters."