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Running Research News And Events
November 09, 2011
How Running Affects Sleep (and Vice Versa)
Adequate Regenerative Sleep is Critical for Good Running and Health
Dedicated distance runners leave no stone unturned in their eternal quest for improvement, showing discipline far beyond what one would expect from most recreational athletes. They slog long miles on sore legs in nasty weather, sprint around the track doing interval workouts, buy the best high tech running shoes, and drink protein laced sports drinks after training. They pump weights diligently, pay good money for coaching schedules, and avidly consume running books and magazines.
Despite this extraordinary dedication, most runners grossly neglect an aspect of training and recovery that would seem to be commonsense- sleep. Getting adequate sleep is one component of the training and recovery cycle that is readily correctible. In fact, it’s indispensable. One of the fundamental rules of recovery is getting enough sleep to allow the body to repair itself.
Yet, a look at the facts about our appalling sleep habits in the U.S.A. (Box 1) convinces me that we need to emphasize the importance of runners getting adequate sleep far more stringently than is currently being practiced by coaches and exercise scientists. I also strongly suspect that other westernized countries suffer from similar levels of sleep afflictions.
Amazingly, while researching this topic I found that most books on running, written by the “experts”, either completely neglect to mention the restorative powers of sleep, or at best pay only lip service to its importance. Only three contemporary running books acknowledge, at a depth more than the standard banal “make an effort to get adequate sleep”, how critical sleep is for runners. Moreover, none of the several dozen books on running that I examined based their superficial recommendations for sleep on any research—certainly no studies were quoted. Perhaps the authors thought getting enough sleep is so obvious that it only needs passing mention?
Sleep is not just something that’s “good to do”, but something that will help our bodies recover faster from running workouts. In addition, many medical research papers show that getting adequate sleep reduces our chances of contracting diseases like cancer, heart disease, heart attacks, high blood pressure, and diabetes. Getting enough sleep also prevents a general impairment of our immune system.
So what does research tell us about running and sleep? In particular, does sleep improve, and does sleep loss affect running performance? We’ll take a look at these questions and finish up by reviewing how much sleep we need and some bedtime tips on how to sleep better and deeper.
Does running improve sleep quality?
People who exercise claim they fall asleep faster, have deeper sleep, wake up less often, and feel less tired during the day. Although these claims are difficult to verify, scientists have shown that people who exercise regularly and intensely spend more time in stage 3 and 4 slow-wave sleep (O’Connor et al. 1995, Kubitz et al. 1996). Trinder et al. (1985) for example, found that fit runners, who average 45 miles/week, spend 87 minutes in slow-wave sleep, 13 minutes or 18% longer than deconditioned people.
Brassington et al. (1995) concluded that physically active older men and women slept longer, took less time to fall asleep, and were more alert during the day than sedentary older people. Sherrill et al. (1998) studied 722 adults and found that men and women who exercised regularly had fewer sleep disorders. G. Passoss (in her presentation at the 2008 Annual Meeting of Associated Professional Sleep Societies) stated that patients with chronic insomnia who did moderate aerobic exercise drifted off to sleep 54% faster than other groups, and slept 37% longer (Passoss 2008).
Several other studies have shown that when people first take up running (and other endurance sports), their sleep quality is improved, and that exercising longer than 1 hour further improves sleep quality (Youngsted 1997, Youngsted et al. 1997). Shapiro et al (1984) found that the sleep quality of army recruits improved during 18 weeks of basic training, with most positive effects occurring in the first 9 weeks. A caveat here though; severe and prolonged exercise such as that experienced in ultrarunning and marathon events, may actually disrupt sleep (Montgomery et al. 1985).
What effects does exercise intensity have on sleep?
A few research papers discovered that higher intensity exercise that causes sweating promotes a better quality of sleep than low-intensity exercise (O’Connor et al. 1995, Youngsted 1997). Perhaps this is because sweating causes the body to cool rapidly, which bring us closer to the lower temperatures we experience during slow wave sleep. Thus, we transition into slow wave sleep more quickly because of this cooling effect.
When is the best time of day to run to ensure good sleep?
There is debate over this issue. Running intensely for 20-30 minutes raises your body temperature at least 2 degrees. Doing this immediately before sleep will delay your transition to deeper sleep because it takes 4-5 hours to cool back down. For this reason, it’s recommended that you exercise no closer than 3-4 hours before bedtime, and some coaches say 6 hours before. This is good advice when you consider that some exercise scientists believe that running too close to bedtime would leave the sympathetic nervous system stimulated for several hours, making it harder for you to get to sleep.
A study by Tworoger et al. (2003) at the Fred Hutchinson Cancer Research Center in Seattle found that an hour of walking every morning relieves many sleep problems in older women (50-75 years). Women averaging 3.5 to 4 hours of morning exercise a week got to sleep earlier, and did not experience as many sleep problems, as the evening exercise group. Morning exercise appears to set our circadian rhythms to stay awake during the day, and cause sleepiness at night.
Where does all this research leave us? A comprehensive meta-analysis of sleep and exercise research by Kubitz et al. (1996) found that exercisers fell asleep faster, and sleep longer and deeper than non-exercisers. As for the question of whether you should work out in the morning, afternoon, or evening; I’d recommend you find what works best for you by trial and error.
How does sleep repair the body?
We sleep in 4 stages, alternating between non-rapid eye movement (NREM) and rapid eye movement (REM). Each sleep cycle takes about 90 minutes. The average adult sleeps about 7.5 hours, or five full cycles, with 20% of that time in REM. Anabolism (repair) takes place during the four stages of sleep (Table 1), but particularly in stages 3 and 4.
Table 1. The four stages of sleep
Stage 1 Transitional, light sleep, with slowing down of the brain activity and vital signs, and dreamlike thoughts.
Stage 2 Lighter deep sleep and slower vital signs, lasting about 30 minutes in adults. We spend about 50% of our sleep time in this stage.
Stage 3 & 4 (Slow-wave, delta sleep) Deep sleep with depressed vital signs and slow, low frequency, high amplitude brain activity (delta waves), leading to Rapid Eye Movement (REM). During REM our eyes dart about rapidly and we have vivid dreams. General protein synthesis, cell growth and division, and tissue repair and growth take place during all four stages of sleep, but mainly during slow-wave delta sleep. The release of growth hormone for cell growth is at its circadian peak during delta sleep, and most scientists agree that delta sleep activity reflects the metabolic activity and energy expended by the athlete during the previous day (Shapiro et al. 1984).
Does sleep loss impair running performance?
Sleep loss has been shown to cause a cascade of unpleasant effects ranging from impaired endocrine and immune system function to reductions in memory, concentration and cognitive performance. Social consequences of sleeplessness appear to be irritability and inability to enjoy family and social relationships. But what happens when we lose sleep the night before a race? Will this adversely affect our running performance?
Researchers of sleep deprivation have looked at its effects on VO2 max, treadmill running and walking to exhaustion, respiration levels, maximal heart rate, and other parameters of endurance exercise. Generally, sleep loss ranging from 4-60 hours does not impair performance in short term and unskilled endurance activities like running, rowing and swimming (e.g., Pilcher et al. 1996, VanHelder et al. 1989). The adrenalin rush of competition (aka “arousal”) appears to override any negative physical consequences of sleep deprivation. But there does appear to be great variability in the individual’s response to sleep deprivation. Some people are highly susceptible to sleep loss, while others seem to be resistant to it. Martin et al. (1981) highlighted this variability when they walked sleep-deprived subjects to exhaustion on a treadmill. Two sleep-deprived subjects actually increased their walking time to exhaustion, 4 showed no significant change, and 4 subjects showed a large decline in time to exhaustion! This is something you need to bear in mind if you anticipate running with little or no sleep. If you’re susceptible to sleep loss, expect to perform below your best.
Additionally, sleep-deprived endurance athletes often complain that their races feel much harder than usual (Bond et al. 1986), so don’t expect to feel good during or after the race if you’re sleep-deprived. Another disadvantage of sleep deprivation for distance runners is that it takes longer to recover from races due to elevated stress hormone levels. Studies by Kuhn et al. (1973), Opstad et al. (1980), Hart (1983), Jezova et al. (1985), and VanHelder and Radomski (1989) have demonstrated that catecholamine and cortisol levels are increased with the combination of sleep deprivation and exercise, while only a few studies have found no effect of sleep deprivation on those same hormones.
Another concern is that our ability to dissipate heat may be affected by sleep loss. Dr. Michael Sawka, at the U.S. Army Research and Development Center, Natick, Massachusetts, believes that “sleep loss can depress the body’s thermoregulatory system by reducing our ability to sweat during exercise”—potentially something that could impair the endurance athlete’s performance significantly (Nash 1985).
Many studies have investigated the effects of sleep deprivation on non-endurance activities like carrying sandbags, carrying loads on a wheelbarrow, and walking with a backpack; and all these activities appear to be adversely affected, i.e., performance was reduced. Sleep deprivation also impairs sports that require high levels of motor skills and coordination, but these activities are of limited interest to runners unless you happen to do marathons while juggling or performing mathematical equations. So if you miss several hours of sleep for a night or two before your race, your performance is not likely to be impacted unless you are particularly susceptible to sleep deprivation.
How much sleep do we need?
Adults need between 7.5 to 8 hours of sleep a night. The U.S.A. is one of the most sleep-deprived nations in the world with 71% of its population sleeping less then 7.5 hours a night. The average American only has 7 hours of sleep, with one third of us averaging 6 hours or less per night. Why is there a high percentage of sleep-deprived Americans? Many of us just don’t want to turn off the lights, and research shows that artificial light disrupts sleep by interfering with our circadian rhythms.
To nap or not to nap?
Another area of debate by scientists is the issue of napping. Should you take naps during the day or avoid them because they may keep you awake at night? The anti-nappers claim that if you’re sleepy during the day, you’re not getting enough sleep at nighttime—and they have a good point. Apparently 80% of nappers sleep worse after an afternoon nap, and only 20% sleep better. Most readers will know whether napping degrades your nighttime sleep or not.
Waterhouse et al. (2007) concluded that a post-lunch nap improves alertness and aspects of physical and mental performance following partial sleep loss, and thus may be of use to athletes who have lost sleep during training or before competition. But, if you must nap, make sure you do this at the same time every day, and for no longer than one hour. Do not nap any later than 3 p.m.
Bedtime Tips—How to Sleep Well
Preparation for sleep
Maintain a regular bed and wake time schedule, including on weekends.
Establish a regular, relaxing bedtime routine (e.g., reading in bed, relaxing in a hot bath 1-2 hours before bedtime, meditation, breathing exercises, etc.).
Skip watching the news before bedtime if you find that it causes you to feel uneasy or stress. Likewise avoid activities like watching TV, eating, planning or problem solving while in bed. We tend to fall asleep if our body is relaxed and our mind is not focused on anything exciting or stressful.
Avoid caffeine and nicotine close to bedtime (some say from noon on). This includes coffee, tea, soft drinks, and chocolate.
Avoid alcohol because it causes sleep disruption during the night.
Avoid heavy meals close to bedtime.
Exercise regularly, but avoid exercising heavily within 3 hours of bedtime.
Your sleeping environment
Create an environment that encourages good sleep: dark room (use blackout shades), absolute quiet, cool and comfortable temperature.
Blue light, emitted from computers, televisions, digital clocks and DVD players interrupt your body clock, or circadian rhythms; cover them at night.
See your physician or sleep disorder specialist if you think you have a sleep disorder.
If you wake up, stay in bed, close your eyes and relax. If you still cannot sleep, read a book.
Avoid oversleeping, as it causes shallow, disturbed sleep.
A good mattress is essential for good sleep.
A German study in 2001 found that a medium-firm pillow significantly improves sleep. Your pillow must support your head without burying it.
Cover your nonallergenic foam pillow with a dust mite protective cover. Put your pillow into the dryer every few months to kill dust mites, and replace it every two years.
People suffering from sleep deprivation have been found to respond well to full spectrum lights (10,000 lux fluorescent lights), for 30-minute sessions early in the morning. This helps them get to sleep earlier and stay asleep longer. It is believed that the regular exposure to this light triggers the nighttime release of melatonin. This important hormone helps maintain your body’s internal clock, giving you that sleepy feeling in the evenings.
Perhaps it’s time you evaluated your sleep habits to see whether you are allowing yourself enough sleep for maximum running performance. Remember, the constant cycle of overload, followed by adaptation and recovery is what improves your running, week-by-week and month-by-month. It’s critical that you give yourself enough sleep to recover from your training and racing. For good sleep, you need at least 30 minutes of moderate aerobic exercise, five or more days each week, and running is a perfect mode of aerobic exercise.
Consider these disturbing data about our sleeping habits.
70- 80 million Americans have serious, incapacitating sleep problems.
62% of Americans have problems sleeping a few nights a week.
20% - 40% (about 40 million) of Americans have insomnia, sleep apnea, or restless leg syndrome.
40% of adults are so sleep deprived during the day that it interferes with their daily activities.
Nearly half of older adult Americans say they do not get a solid night’s sleep.
40% of insomniacs self medicate themselves with over the counter meds or alcohol.
Sleep loss and disturbances play a major role in 100,000 automobile accidents each year.
Consumers spend $1.1 billion each year on products used to promote sleep.
Costs of insomnia to industry are estimated at $45 billion annually, in terms of decreased productivity and accidents.