Sleep and Sports Performance
Most of us fail to get enough sleep, at least as much sleep as the experts say that we should enjoy.
Nevertheless, most of us manage to make it through the day without too much difficulty, though of course continual sleep deprivation can be damaging to our physical and mental health. In this article on sleep, we will look at some of the research that has been carried out on how not getting enough sleep can impact on the performance of elite athletes, and some of the current thinking on what happens when we sleep and when we don’t get enough of it.
Sleep deprivation and sports performance
Most people need between 7 and 8.5 hours sleep. Many studies have been carried out on how sleep affects sports performance. In one of these the effects of various degrees of sleep deprivation on judo players was examined with some interesting results (N Souissi et. al.,2013).
Some players received a full night’s sleep of 7.5 hours, others received just 4 hours sleep at the beginning of the night, and another group received 4 hours sleep at the end of the night. Tests on strength and cardio power were then carried out at 9.00 am and 4.00 pm the following day.
Athletes that received a full night’s sleep athletes performed significantly better at 4.00 pm then they did at 9.00 am, and the performance of the other two groups were reduced to a similar degree than they would have been if they had just competed in a judo match. The group that slept earlier performed even worse at 4.00 pm than they had at 9.00 am.
The somewhat startling conclusion is that loosing just a few hours’ sleep is as exhausting as competing in a match, and that effects get worse the longer the time delay between sleeping and competition.
The effect of extended sleep
In another study, this time on basketball players, the effect of prolonged sleep was investigated (Mah CD, Mah KE, Kezirian EJ, & Dement WC 2011).
Over several weeks, the sleep time of the athletes was increased so that they slept for at least 10 hours a night. The result was that every basketball player in the group could sprint faster, shoot more accurately, has a faster reaction time, felt better, and showed improved vigour and fatigue scores.
Cat naps
Enjoying 10 hours a sleep every night is not a luxury many athletes can afford, so is taking a cat nap a viable alternative?
To test this out, a previous study by Waterhouse (2007) showed that athletes who received just four hours sleep but were permitted a 30-minute afternoon nap had improved alertness, faster reaction time, lower heart rate, better short memory, and could sprint faster than those who were similarly sleep deprived but did not take a cat nap.
What happens when we sleep?
There are distinct patterns in the way we sleep. Sleep patterns alternate between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep in 90 minute cycles, with NREM sleep talking up around 75% of the total sleep time. We begin with NREM sleep, which has four stages:
Stage 1 – beginning to fall asleep and light sleep from which it is easy to be awoken.
Stage 2 – sleep onset, heart rate slows and body temperature falls
Stages 3 and 4 – deep sleep which is the most restorative; blood pressure falls, breathing is slower, and muscles are relaxed. The blood supply to the muscles increases and repairs to tissue and new tissue generation occur. Energy levels are restored and several hormones, including the growth hormone, are released.
During REM sleep, which starts around 90 minutes after falling asleep, the brain is active and dreams occur. It lasts from around 10 minutes to an hour during which time the brain patterns resemble those when awake. Heart and respiration rates increase, and the major muscles are paralysed.
Elite Athletes and Jet Lag
Elite athletes frequently travel across time zones, and it has been demonstrated that this can result in a physical and emotional burden that can negatively affect their performance (Lee A, Galvez JC, 2012).
Jet lag is a sleep disorder the symptoms of which include reduced daytime function, a general malaise, and other somatic problems such as disruption if the gastrointestinal system.
It occurs because the body’s circadian rhythm is out of sync with the local time zone. While the sleep-wake cycle can recover in 2 to 3 days, other bodily cycles such as core body temperature can take 8 to 10 days.
Some of the effects that particularly affect athletes are:
• Cognitive Performance – mood and mental performance deteriorates, errors and injuries increase, general feeling of lethargy reduced motivation.
• Physical Performance – reported effects include a decrease in arm and elbow flexion strength and poorer sprint performance in swimmers; decreased leg and back strength, lower reaction times in Olympic athletes.
• Team Performance – this has been demonstrated amongst NFL teams where West Coast teams beat East Coast teams consistently in evening games.
Finally
Proper sleep is essential to achieving optimal athletic performance so sleep loss, whatever its cause, is not something that athletes should ignore. Various treatments are available for sleeping disorders, and exercise can help resynchronise core temperature and heart rate circadian rhythms to reduce the effects of jet lag.
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References
Lee A, Galvez JC, (2012). Jet Lag in Athletes, Sports Health. 2012 May; 4(3): 211–216.
Mah CD, Mah KE, Kezirian EJ, & Dement WC (2011). The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep, 34 (7), 943-50 PMID: 21731144
N Souissi et. al. (2013). “Effects of Time-of-Day and Partial Sleep Deprivation on Short-Term Maximal Performances of Judo Competitors,” Journal of Strength and Conditioning Research, 27(9)
Waterhouse, J., Atkinson, G., Edwards, B., & Reilly, T. (2007). The role of a short post-lunch nap in improving cognitive, motor, and sprint performance in participants with partial sleep deprivation Journal of Sports Sciences, 25 (14), 1557-1566
