Sleep and exercise advice
Dedicated runners, swimmers and cyclists 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 and in swimming pools, sprint around the track doing interval workouts, buy the best high-tech running shoes and cycling gear and drink protein-laced sports drinks after training.
Despite this extraordinary dedication, most endurance athletes grossly neglect an aspect of training and recovery that would seem to be common sense: sleep. Getting adequate sleep is one component of the training and recovery cycle that is indispensable. One of the fundamental rules of recovery is getting enough sleep to allow the body to repair itself. Yet, over half the people in westernised countries have difficulty sleeping at least a few nights each week, or have sleep disorders of varying severity.
Most sports training books written by the “experts” completely neglect to mention the restorative powers of sleep, or pay only lip service to its importance, with the standard banal “make an effort to get adequate sleep” comment.
Sleep is not just something you should “make an effort” to do; it speeds your recovery from training workouts. Many medical research papers show that getting adequate sleep reduces your chances of contracting diseases like obesity, cancer, heart disease, high blood pressure and diabetes, and prevents a general impairment of your immune system.
What, then, does the research tell us about endurance training and sleep? In particular, athletes are curious as to whether their sport improves their sleep and are concerned about whether sleep loss affects their performance.
Exercise & 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 intensively spend more time in stage three and four slow-wave sleep. A research paper by Trinder, for example, found that fit runners, who averaged 72km/week, spent 87 minutes in slow-wave sleep — 13 minutes or 18 per cent longer than deconditioned people.
Brassington 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’s study of 722 adults showed 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 per cent faster than other groups and slept 37 per cent longer.
Several other studies show that when we first take up endurance training, our sleep quality is improved and that exercising longer than one hour further improves sleep quality. Shapiro’s study of army recruits found their sleep quality improved during 18 weeks of basic training, with most positive effects occurring in the first nine weeks. There’s a caveat here, though: severe and prolonged exercise such as that experienced in ultrarunning and marathon events actually disrupts sleep.
A few research papers discovered that higher-intensity exercise that causes sweating promoted a better quality of sleep than low-intensity exercise. 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 the cooling effect transitions us into slow-wave sleep quicker.
Timing your training
There is debate over the best of time of day to train to maximise sleep quality. Exercising intensively for 20–30 minutes raises your body temperature. Doing this immediately before sleep will delay your transition to deeper sleep because it takes four to five hours to cool down. For this reason, it’s recommended that you exercise no closer than three to four hours before bedtime; some coaches even say six hours before. This is good advice when you consider that exercise scientists think training too close to bedtime leaves the sympathetic nervous system stimulated for several hours, making it harder for us to get to sleep.
A study conducted by the Fred Hutchinson Cancer Research Center in Seattle, US, found that an hour of walking every morning relieves many sleep problems in older women (50-75 years). The women averaging 3.5 to 4 hours a week of morning exercise 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 causes sleepiness at night.
Where does all this research leave us? The overall message is clear. A comprehensive meta-analysis of sleep and exercise research by Kubitz concluded that exercisers fall asleep faster, and sleep longer and deeper than non-exercisers. As for whether you should work out in the morning, afternoon, or evening, you will need to find what works best for you by trial and error.
We sleep in four 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 per cent of that time in REM. Anabolism (repair) takes place during the four stages of sleep but particularly in stages three and four.
Sleep loss & performance
Sleep loss has been shown to cause a cascade of undesirable 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 an inability to enjoy family and social relationships. However, what happens when you lose sleep the night before a competition? Will this adversely affect your 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, the data shows that sleep loss ranging from four to 60 hours does not impair performance in short-term, unskilled endurance activities such as running, rowing and swimming. The adrenalin rush of competition (AKA “arousal”) appears to override any negative physical consequences of sleep deprivation.
However, there does appear to be great variability in individual response to sleep deprivation. Some people are highly susceptible to sleep loss, while others seem to be resistant to it. A study by Martin and associates 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, four showed no significant change and four subjects showed a large decline in time to exhaustion. This is something you need to bear in mind if you anticipate competing 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 subjectively, their races feel much harder than usual, so don’t expect to feel good during or after the race. Another disadvantage of sleep deprivation is it takes longer to recover from races due to elevated stress hormone levels. Several studies show that levels of our stress hormones, catecholamine and cortisol, are increased with the combination of sleep deprivation and exercise.
Another concern is that our ability to dissipate heat may be affected by sleep loss. Dr Michael Sawka at the US Army Research and Development Center, Natick, Mass., believes “sleep loss can depress the body’s thermoregulatory system by reducing our ability to sweat during exercise” — something of great concern to the endurance athlete.
Many studies have investigated the effects of sleep deprivation on non-endurance sports. It appears that sleep deprivation does impair sports that require high levels of motor skills and co-ordination. 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 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 you need?
Adults need between 7.5 and eight hours of sleep a night. Most of us average only seven hours of sleep, with one-third of us averaging six hours or less per night.
To nap or not to nap?
Another area of debate among scientists is the issue of napping. Should you take naps during the day or avoid them because they may keep you awake at night? One study found that 80 per cent of people sleep worse after an afternoon nap, while only 20 per cent sleep better. Most readers will know whether napping degrades your night-time sleep or not.
A study by Waterhouse 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 3pm.
Preparing for sleep will allow you to sleep as well as possible. Here are some tips for that preparation:
- Maintain a regular bed- and wake-time schedule, including on weekends.
- Establish a regular, relaxing bedtime routine (eg 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 it causes you to feel uneasy or stressed. Likewise, avoid activities such as watching TV, eating, planning or problem solving while in bed. We tend to fall asleep if our bodies are relaxed and our minds are not focused on anything exciting.
- 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 three hours of bedtime.
Once you’re in your bedroom, create an environment that encourages good sleep: a dark room (use blackout shades), absolute quiet and a cool, comfortable temperature. Blue light emitted from computers, televisions, digital clocks and DVD players interrupts your body clock or circadian rhythms. Cover them at night.
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 non-allergenic foam pillow with a dustmite-protective cover. Put your pillow into the dryer every few months to kill dustmites, and replace it every two years.
Perhaps it’s time you evaluated your sleep habits to see whether you are allowing yourself enough sleep for maximum sports performance. Remember, the constant cycle of overload followed by adaptation and recovery is what improves your running, swimming or cycling, 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.
Roy Stevenson has a Masters degree in exercise physiology and coaching from Ohio University. He teaches exercise science at Seattle University in Washington State, US. W: roy-stevenson.com
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