Sleep is essential for health and quality of life, but it is also determinant for recovery and adaptions to exercise. The duration of sleep and its quality need to be considered in the general population, but especially in athletes, as they are associated with a better performance and a lower risk of injury and illness.
The amount of sleep recommended by the American Academy of Sleep Medicine oscillates between 7 and 9 h for adults, and 8 and 10 h for adolescents. Although these are general recommendations and there are variations among individuals, it has been suggested that athletes may need more sleep for adequate recovery. Adequate sleep is so important that people over 45 years old sleeping less than 5 hours/night have a higher mortality risk. This risk was also increased in people usually sleeping more than 10 hours/night.
As suggested earlier, the quality of sleep is also important. Adult humans usually sleep in a single and continuous bout, alternating cyclically between two states: nonrapid eye movement sleep, or NREM, and rapid eye movement sleep, or REM.
These phases can be distinguished using polysomnography, a technique that measures simultaneously the electroencephalogram (EEG), and ocular and muscular patterns. The NREM phases, that account for about 75% night´s sleep, are characterised for the inactivity and a slowing in the frequency of the EEG. On the contrary during the REM phases (approximately 25% of night´s sleep) there is an increase in the neuronal firing rate, metabolic rate and blood flow.
Sleepiness during the day is usually a symptom of inadequate sleep a night. For a normal adult it usually takes 10-20 minutes to enter the sleep, while a sleep deprived person can fall asleep in less than 5 minutes. Are you one of these? Keep reading.
The circadian rhythm is a period of about 24 hours with oscillations that accomplish the sleep and awake phases. All organisms exhibit these circadian behavioural or physiological rhythms. In humans the pacemaker for these cycles is in the hypothalamus area of the brain, and it needs to be synchronized daily. Light and an organized schedule of meal and bed times are good synchronizers of the human circadian pacemaker.
Sleep disturbances are strongly associated, among others, to mental illnesses, learning disabilities in children, and higher rates of gastrointestinal and cardiovascular complaints in shift workers or air travellers flying across multiple time zones. Moderate exercise appears as the most important sleep-promoting factor and an attractive alternative for the treatment of insomnia.
To test the effects of physical inactivity on sleep, healthy young individuals were confined to bed for 60 hours, in a sound attenuated room with no access to daylight or information about day time, and prevented from activities such as exercise, TV, reading, writing or listening to music. In these conditions the typical continuous sleeping period of 8h was replaced by short sleep bouts of around 3h throughout the day.
During sleep deprivation studies, vigorous exercise was always able to overcome sleepiness, although the sleep effects post-exercise could be enhanced. Although at moderate levels exercise may be a sleep-promoting factor, training volumes and schedules can have potentially negative effects on sleep, especially in young athletes, which many times must accommodate training and study, sacrificing sleeping time.
Competition also can have negative effects on sleep, due to long travel, that affect circadian rhythms, and increased levels of anxiety and stress. There have been reported insomnia symptoms prior to competition in as many as 78% of elite athletes. The disruptions affected more women, athletes from individual disciplines, and especially participants of aesthetic disciplines (dance, gymnastics, etc) where success is judged by others.
Also, a lack of sleep correlates with a higher risk of injury. It is not very clear if it is because enhanced fatigue, or impairments in reaction time and cognitive function. Decreased sleep also affects the immunologic system, especially increasing the possibility of infections in the upper respiratory system. In a study, individuals sleeping less than 7 hours were three times more likely to get an infection than those sleeping 8 or more hours.
Proper sleep hygiene should include a sleep-promoting environment: cool, dark, minimal noise and no electronic devices, which could be interfering with the natural melatonin secretion, strongly related with sleep induction. Repetitive schedules, and a short period of relaxation before going to bed may also be helpful. Tobacco and caffeine should be avoided, especially late in the day, as should be sedating medicines, with no proved benefits, but potentially addictive.
During periods of sleep restriction, naps could be helpful in performance enhancement. They should not be very long, to avoid disruptions in nigh time sleep. 30 minutes look as the proper length.
With sleep affecting so directly health and sports performance, it is clear the importance of having adequate resting periods, with the highest possible quality, not only in athletes, but also in general population. With the crazy rhythms of modern life, we are always trying to squeeze the day, many times sacrificing sleeping time in order to get more activities in an already packed schedule. We should consider if that extra time is really used for an important activity, otherwise we could be better sleeping more. Our health and performance would be grateful.
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