To Sleep, Perchance to Grow
Jerry BrainumSnooze or You Lose Muscle, Part 2
In Part 1 of this discussion we saw how lack of sleep negatively affects your anabolic hormones and promotes bodyfat accrual. It also affects your ability to perform.
Sleep and Exercise
Most studies examining the effects of sleep on training have been contradictory, with some showing negative effects, others none. Some trends have become clear, however. For example, studies show that if high-intensity exercise is done in the afternoon, it will adversely affect sleep at night. Low-intensity exercise, however, has no effect on sleep, unless the exercise is prolonged.1 Training in the morning has no effect on sleep.
Overtraining may indirectly affect sleep quality. Studies show that overtrained athletes move around more when they sleep, which can have a disturbing influence. I recall once visiting the home of a well-known professional bodybuilder. I noticed that he had a small Army cot next to a larger bed. “Who sleeps on the cot?” I asked.
“I do,” he replied. “My wife moves around too much when she sleeps, and that keeps me up, hence the cot.” His pragmatic approach made sense to me. It’s underscored by the fact that he’s still married to the same woman nearly 40 years later.
Lack of sleep may affect some forms of exercise more than others. For instance, studies show that partial sleep deprivation led to a lowered maximal oxygen intake, along with higher accumulation of lactate, a marker of exercise fatigue. Those lacking sleep show higher heart rates and more labored breathing while training. That all points to insufficient sleep adversely affecting endurance, or aerobic, training. The insulin resistance induced by sleep deficiency adds to that effect, as it interferes with glucose use in muscle.
What about weight training? One study examined the effect of exercise—weight training—in depressed older people.2 It featured 32 subjects with an age range of 60 to 84 who engaged in a weight-training program three times a week. Another group didn’t train. Those in the weight group reported improved sleep quality, along with less depression, which itself can interfere with sleep. Because sleep is a particular problem for older people, the study suggests, weight training can help improve their sleep.
Another study had eight male subjects, aged 18 to 24, who slept only three hours a night for three consecutive nights, then had a four-day phase of normal sleep. The segments were separated by 10 days. The men trained on a weight program that included biceps curls, bench presses, leg presses and deadlifts. Initial tests were done to establish maximal lifts. Lack of sleep didn’t affect biceps training but did affect the bench press, leg press and deadlift. The deterioration in performance on those exercises became significant on the second day of sleep deprivation. The implication is that large-muscle-mass exercises are affected more adversely by a lack of sleep than exercise of smaller muscle areas, such as the arms.
Researchers put physical-education students on light exercise in the morning, evening and late evening. Exercising in the late evening resulted in subjective reports of better sleep, along with less daytime sleepiness.4
How can exercise aid sleep? Several mechanisms have been suggested:
• Anxiety reduction. Disturbed sleep is closely associated with anxiety, and anything that reduces anxiety, such as exercise, will help promote sleep.
• Antidepressant effect. Disturbed sleep is a hallmark of mental depression. Since exercise is a natural antidepressant, it can promote sleep. One theory suggests that exercise rapidly relieves depression by suppressing REM, which seems to lower depression. Reducing REM sleep by 25 percent showed significant antidepressant effects.
• Thermogenic effect. Exercise increases slow-wave sleep, possibly due to elevated body temperature. That leads to a lowered body core temperature, which is a sleep signal. Studies show that a drop in body temperature of one degree near bedtime is an internal signal that triggers the drive to fall asleep. For those who don’t work out, taking a hot bath about an hour prior to bedtime can trigger the sleep response because of a rapid core temperature lowering that begins as soon as you step out of the bath.