More threads by David Baxter PhD

David Baxter PhD

Late Founder
Sleep After Hard Workouts? You Must Be Dreaming
By GINA KOLATA, New York Times
September 13, 2007

WHEN Jennifer Davis, my partner for long runs, was in college about 15 years ago, she had a real problem staying awake in her classes. The reason, she said, were those long, grueling workouts with the Dartmouth crew early in the day.

?Those are the only memories I have of totally falling asleep in lectures,? said Ms. Davis, a physical chemist living in Montgomery, N.J. ?My notes from biology consist largely of squiggly lines meandering down the page of my notebook.?

It?s one of the mysteries of sleep: Why is it that mild exercise can be invigorating, but strenuous endurance exercise ? whether it?s crew practice, long runs as training for a marathon or juggling back-to-back workouts to prepare for a triathlon ? makes people groggy?

Elite marathoners know that hunger for sleep all too well.

Deena Kastor, who won the London Marathon last year and set an American record, said she sleeps 10 hours at night and takes a two-hour nap every afternoon. Steven Spence, a marathoner who won a bronze medal at the 1991 world championships in Tokyo, had the same sleep habits when he was training.

?I would be sleeping about half of my life,? Mr. Spence said.

Researchers say the science behind that sleepiness is poorly understood. Most studies ask other questions, like how sleep affects memory and thinking abilities, and suggest, for example, that it may help people consolidate memories. Of course, no one ever thought they had to sleep for 12 hours because they were studying so hard.

There are no studies of large groups of endurance athletes, asking whether they needed more sleep and, if so, why, said Dr. Alex Chediak, president of the American Academy of Sleep Medicine and chief of the Sleep Disorders Center at Mount Sinai Medical Center in Miami Beach.

In fact, he said, to his knowledge, ?there is not even a study where a long distance runner was allowed to do his or her thing and then studied for sleep before and sleep after.?

Most sleep studies are more practical, Dr. Chediak explained, with a goal of helping people in the general population. ?Runners are more of a curiosity,? he said. And because intense endurance exercise isn?t what most exercisers do, it is not even feasible to reason by inference.

For example, sleep specialists often tell people with insomnia to exercise five to six hours before bedtime. The mild exercise raises the body?s core temperature. When the temperature falls again a few hours later, that signals the body to sleep.

But that is a different sort of exercise from what endurance athletes do, and so what happens to marathoners-in-training must have another explanation. One possibility, Dr. Chediak said, is that cytokines ? hormones that signal the immune system ? are making these athletes sleep so much.

Exercise, Dr. Chediak said, prompts muscles to release two cytokines, interleukin 6 and tumor necrosis factor alpha, that make people drowsy and prolong the time they remain sleeping. In fact, those cytokines also are released when people have a cold or infection, which is why people sleep so much when they are ill.

It turns out that the single most important factor for increasing the release of those two cytokines is increasing the duration and intensity of exercise, Dr. Chediak said. And, he noted, that?s what is happening when endurance athletes train. ?A sprint will not get you as great an effect,? he said.

On the other hand, he cautioned, the cytokine hypothesis is based on extrapolations from other data and animal studies.

But spending half their lives slumbering is only part of the sleep equation for athletes. They also have the opposite problem: they have trouble falling asleep the night before a big race.

It?s not clear whether a sleepless night before a race affects athletic performance, Dr. Chediak said. Rigorous studies have not been done. He suspects that the main effect of pre-race insomnia will be on mental performance, he said.

But elite athletes can?t take that chance. And some amateurs gunning for a personal record don?t want to risk falling short, either. The trick is to be well prepared, said Meb Keflezighi, the United States marathon runner who won a silver medal at the 2004 Athens Olympics. In the weeks leading up to a race, he will have trained and visualized the course, planning his strategy. Finally, when the big day is nigh, he usually can drift off.

At the very least, Mr. Keflezighi said, he has learned to avoid the sort of experience he had in 1996, when he was running a five-kilometer national championship race in Eugene, Ore.

?I told my coach I was going to win it and get the record,? Mr. Keflezighi said. He was so excited that he tossed and turned all night before the race, sleepless, rehearsing the race in his mind.

The next day, when the starting gun went off, Mr. Keflezighi did his best ? and came in ninth. The problem, he says now, was what happened the night before, when he was lying in bed:

?I already ran that race ? in my head.?
Very interesting. I have noticed this myself. I often do a 20 min. run first thing in the morning and this really wakes me up. Four hours of swim practice wakes me up also for about an hour and then I need a nap. Not long usually - Maybe for an hour or an hour and a half.
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