The importance of sleep for athletes
Most of us spend approximately one third of our lives asleep, and it is easy to view this as time that is ‘wasted’, with little benefit for training or competing. However, sleep is an essential part of an athlete’s training, and is the time when many of the physiological adaptions to the stimulus of training takes place.
The human ‘body clock’ is regulated by a series of cycles known as the ‘circadian rhythm’, which determines areas such as digestion, hunger, body temperature and heart rate, as well as the time of day when we sleep.
Sleep scientists have found that we have a series of sleep phases each lasting approximately 90 minutes, which initially take us into alternating periods of deeper and lighter sleep, before gradually emerging to a lighter pre-awakening stage characterized by rapid eye movement, or REM.
It is during the deeper, non-REM phases, where sleep does most to help to support athletes. One of the first things to occur is the redistribution of blood supply, with over 40 per cent of the blood that normally goes to the brain during waking hours diverted to the muscles.
At the same time, hormones are released that help with the repair and growth of tissues, something that is essential after a long or intensive run or race. One of the main hormones that is released is human growth hormone, which plays an essential part in rebuilding and developing the proteins that constitute the muscle fibres that will have been repeatedly exposed to the rigours and stimulus of running. Muscle and liver glycogen stores will also be replenished, ensuring that energy reserves are at full capacity in time for the next run.
There is also evidence to suggest that sleep helps to support the body’s immune system, something that is crucial if illness and infections are to be avoided. While asleep, the body releases proteins called cytokines.
Some of these help to promote sleep, while others are important in the fight against inflammation and infection, and to combat the physical stresses that are caused as a result of training.
Scientists and medical practitioners often recommend exercise during the daytime as a means of enhancing sleep quality, since the body responds to the need to recover and repair by increasing sleeping time and quality. However, since sleep involves a reduction in heart rate, core temperature and blood pressure, it is not advisable to finish a training session or run just before going to bed, because the residual effects of an elevated metabolic rate will make it much harder to fall asleep.
While there are clear and unequivocal benefits from sleep for athletes, continuous sleep loss can be a major issue, with the risk of injury, illness and fatigue all increasing. The amount of sleep that we require varies from one person to another, with 7–8 hours being the norm for most adults, athletes sometimes needing slightly more. So sleep is as much a part of your training and preparation as your weekly sessions, and without the restorative effects of sleep it would be impossible to train effectively and compete.
Nevertheless, few athletes get a sound night’s sleep before a major competition, due to the combined effects of anxiety and the need to wake at an early hour to get to the start line.
While it is easy to panic if you are not sleeping well on the night before a race, I have never yet seen an athlete fall asleep while racing or competing. Keep things in perspective.
» Professor John Brewer is head of the school of sport, health and applied science at St Mary’s University in Twickenham and author of Run Smart: Using Science to Improve Performance and Expose Marathon Running’s Greatest Myths (Bloomsbury; £12.99)
