After a bad night’s sleep, nothing feels right. The mind is fuzzy and the muscles are sapped. Often the last thing you want to do is work up a sweat. You might find yourself wondering what kind of workout you should do, and if it’s better to put it off until you’re not quite so groggy.
A recent paper from researchers in Australia suggests that exercisers functioning on little sleep can get the most out of a workout by doing it earlier in the day and focusing on strength and endurance, rather than complex skills. The meta-analysis, published in the November issue of Sports Medicine, is the latest in a string of studies examining the link between sleep and athletic performance.
“The key factor is, ‘What was the type of sleep loss that you had?’ And then, ‘When are you going to train and what are you going to train?’” said Jonathan Craven, a graduate student at Griffith University in Queensland and one of the authors of the paper.
The type of workout makes a difference.
The meta-analysis, which combined data from 77 studies, examined the effect of a single night of diminished sleep — meaning fewer than six hours — on strength, endurance and athletic skill the next day. As with previous studies, the Australian team found that poor sleep blunts most aspects of athletic performance, like speed, power, endurance and complex skills, such as hitting a tennis ball or spiking a volleyball.
The scientists put each exerciser’s performance on a percentage scale. They found that after poor sleep, complex skills declined as much as 23 percent, while strength and endurance only saw losses of up to 5 and 8 percent, compared to workouts performed after a full night’s sleep. In other words, after a bad night of sleep, some subjects’ ability to hit the bull’s-eye in an archery session was far more affected than others’ ability to run at a certain speed or lift a certain amount of weight.
“The longer an activity, or the more an activity requires you to use your brain, the more likely you are going to have a negative effect of sleep deprivation,” said Shona Halson, a researcher at the Australian Catholic University in Brisbane, Australia, who studies the effect of sleep deprivation in athletes and was not involved in the study. “If you are trying to do a 100-meter sprint, and you are sleep-deprived, you are probably not going to be as affected as someone who has got to run a marathon or play tennis.”
Timing is everything.
Researchers found that working out earlier in the day, just after waking up, helped minimize the effects of sleep loss, and the negative effects slowly increased as the day went on.
“If you have a choice and you are sleep-deprived, you are probably better off training in the morning,” Dr. Halson said.
For example, athletes’ performance on complex skills dropped by 14 percent if the workout was done in the morning after a poor night’s sleep and 23 percent by the evening.
Weight lifters performed 2 percent worse than usual during a morning workout, while waiting until evening reduced their performance by 5 percent. The study showed this effect was stronger among exercisers who lost sleep by getting up too early rather than going to bed too late. The researchers suggest that athletes traveling for competitions might be better off traveling at night and sleeping nearby instead of getting up early.
The reason for this performance decline is related to the body’s circadian rhythm, which naturally makes people feel more alert when it’s light outside and tired when it’s dark. The body releases adrenaline — “your endogenous energy drink” — in response to morning light, said Dr. Virend Somers, a cardiologist who studies the effect of sleep loss at the Mayo Clinic.
And adenosine, a chemical that creates a feeling of sleepiness, tends to be lowest in the body just after waking up, increasing as the day wears on, Dr. Halson said — the more adenosine in your body, the more tired you feel.
She emphasized that one bad night of sleep doesn’t mean you should cancel your workout. If you can’t exercise in the morning, perhaps skip the tennis match or pickup basketball game, and focus on strength and endurance workouts.
“People have one bad night of sleep all the time,” she said. “One bad day of training doesn’t make you a bad athlete, and that one night of bad sleep doesn’t make you a bad sleeper. It’s the consistency of what you do over time.”
Rachel Fairbank is a freelance science writer based in Texas.