A Good Night's Rest

Finding the balance between sleeping enough and running enough

Studies specifically linking sleep deprivation with performance in endurance events are scarce, but in one of them, published in the British medical journal The Lancet, researchers found that a period of decreased sleep lasting only a few days interfered with glucose metabolism and raised levels of cortisol, a hormone released in response to stress that may interfere with athletic recovery at high serum concentrations. The study suggests that glycogen synthesis is impaired during periods of reduced sleep, meaning an athlete in these conditions is operating with less than a "full tank" and may "bonk" earlier than a well-rested individual.

In addition, levels of human growth hormone (hGH), which is essential for the repair of training-induced soft-tissue breakdown, are at their highest levels during undisturbed sleep. Interruption of deep, or "slow-wave," sleep may lead to prolonged recovery from exercise owing to decreased or absent blood levels of hGH. A study published in the clinical journal Sleep indicates that subjects awakened periodically and thus prevented from accruing 90 minutes of continuous sleep in the course of an evening experienced marked delays in muscle recovery.

Critical Consistency

Along these lines, many athletes and coaches believe that a consistent sleep pattern, not simply the amount of sleep a runner gets, is critical. "A consistent sleep cycle, with a fixed sleep time and a falling asleep ritual, is essential," says Tom Derderian, coach of the Greater Boston Track Club and author of Boston Marathon: A History of the World’s Premier Running Event. "To train at your best you must live like a clock; you must become a clock." Indeed, researchers have found that advancing or delaying the onset of sleep—and thus its various cycles—by three hours leads to performance decline in a number of areas, even when the total time spent sleeping remains unchanged. Based on sleep specialists’ findings, Derderian’s thoughts are right on the money: An optimal night’s sleep apparently depends on a day minimally burdened by stressful factors, a routine bedtime, and a quiet, dark room in which to doze off.

One thing scientists and runners agree on is that the "optimal" amount of sleep varies greatly from runner to runner. "In order to adapt positively to training, it is necessary to obtain adequate amounts of good quality sleep," says former U.S. Olympian and exercise physiologist Pete Pfitzinger, Ph.D., who says he trained best on nine or nine and a half hours of sleep a night. "The required amount appears to differ markedly between runners. Some runners seem to need ten-plus hours per night, while others thrive on seven or eight."