High performance be it in sport or business are highly dependant on a number of things. In sport we call these things 'controllables' or 'uncontrollables'. The 'controllables' are those things that are within the person such a mental, technical, tactical and physical preparation, equipment, nutrition, and sleep. The 'uncontrollables' are those such as winning or losing, the environmental conditions and other people. In sport athlete performances are highly dependant on the sleep-wakefulness circadian (24 hour) rhythm. Sleep is a massive part of our lives and it is recommeded by those that study sleep that anything between 7.5 to 9 or 10 hours is necessary for optimal functioning. However whilst asleep the human organism is totally inefficient, nothing financially or preparitory gets done. This sleep is dedicated to rest and recovery from the other parts of our lives.
Common sense suggests that good physical tiredness creates a good sleep. Many of us have experienced this and probably what I am experiencing in my life at the moment is a lack of physical tiredness (having changed from an active job for the ambulance service to a reletively office based sedentry one). However the research suggests that this is a little more complex than we might think. Klerman and Hilaire (2007) suggest that the sleep-wakefullness cycle is regulated by feedback loops and that one can adversely or positively effect the other. The picture above has been taken from a paper by Damien Davenne (2009) that descirbes this interaction a little more in depth.
Arrow 1 - Most of our basic physiological components of performance (temperature, strength, flebility) have peaks and troughs that follow the circadian pattern. Which gives us an understanding as to why performance peaks in the afternoon and early evening for many. Interestingly vigilance is one of these rhythms although it also has an ultradian rhythm (less that 24 hours). This explain the tiredness we feel in the early afternoon. Much research has been done on the benefits of napping in the afternoon and naps are also show to prevent sleep restriction. A very short (less than 30 mins) and regular nap session at the beginning of each afternoon (Matchock and Mordkoff, 2007) can increase cognitive function.
Arrow 2 - Exercise can be associated with changing the period, phase and amplitude of the circadiate rhythm (Koteja te al., 2003). It is also noteworthy that exercise has been found to counteract the effects of jet lag (Waterhouse et al., 2007). Within those that are highly active it is likely that synchronisation and amplitude of the circadian rhtyme would be higher than in those that are lessa ctive (Waterhouse et al., 2000).
Arrow 3 - There are two types of electrical states during sleep. Slow wave sleep is a state where the brain reduces is activities and neuronal activies becomes synchronised, and high amplitude, low frequency EEG waves in which growth hormones are releassed from the pituitary gland (Weitzman, 1976). During REM sleep the brain is very active and actually the brain is in a near wakefulness state. It is at this time where memory is consoldidated, however the brain is partly disconnected from the body and some brain stem pathways are suppressed. There are hundreds of studies that show there is a decline in performance when sleep is interupted however, mood psychomotor and cognitive function decrease more rapidly that physical effectiveness. For most of us we are never totally exposed to total insomnia however fragmented sleep caused by anxiety, a new environment, travel schedule can reduce performance. Rosekind (2005) went as far as to say that sleep may be the single most important factor in improving peformance to reacha peak level.
Arrow 4 - Those that regularly participate in certain exercise experience a much higher level quality of sleep. Athletes and those that exercise fall asleep quicker, do not wake as much, and have less changes in stages of sleep but a good transition between REM and non REM cycles. The common assumption that exercise before bed increase alertness is still under much debate. Some research suggests that the seratonin increase after exercise increases awakeness for a few hours after exercise however other research contests this evidence. What is agreed that the delay in the sleep wake cycle is a potent as the effect of bright light on waking.
Sleep and exercise are mutually independant but are also influenced by the body clock. Modification of one ultimately influences the other. Performance is dependant on the quality and quantity of sleep that has been taken before competition. Those that are physically active are long sleepers and the body needs this time to grow and repair. During period of training or high stress it is important to respect the amount of sleep needed and allow for spontaneous waking to occur. It is also important to develop an optimal environment (quiet, dark, not to hot and comfortable) and finally a regular sleep schedule, i.e. getting up at the same time everyday is important.
This article is based upon Davenne, D, (2009). Sleep of athletes- problems and possible solutions. Biological Rhythm Research, 40,1, 45:52.
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