Tuesday, February 19, 2008

Sleep, Health and Fitness.

Sleep quality is reflected by the proportions of time we spend in different stages of sleep throughout the night and, more obviously, by the amount of time we spend without waking or being aroused. The proportion of time we spend in each sleep stage is represented by a sleep pattern that is common to the normal human population. However, our sleep patterns can vary as they are influenced by our sleep hygiene, daily level of physical exertion and the state of our physical and mental health.

Sleep hygiene refers to the way we chose to practice our sleep habits and is a very important aspect of health and fitness. Due to the circadian regulation of sleep, consistent bedtimes and sleep duration are of most benefit in order to optimize sleep patterns. Delayed bedtimes or early awakenings that result in partial sleep deprivation can affect mental and physical performance on the following day. Too much or too little sleep can also be counterproductive to daytime performance. Optimal sleep time depends on the individual and the level of physical exertion and stress.

Daily physical exertion increases the amount of time we spend in our deep sleep state. The deep sleep dominates the first third of our nights sleep and represents 10-13 % of the nights sleep in the normal population. Training individuals, especially those engaging in high intensity workouts, can have up to three times the amount of deep sleep, representing 25-35% of the nights sleep. Since growth hormone is facilitated by the neurophysiology of deep sleep it is important that training individuals do not compromise the first third of their nights sleep by delaying their normal bedtime or by sleeping in a potentially arousing environment.

The last third of the nights sleep is dominated by the Rapid Eye Movement (REM) sleep stage. Unless physical exertion raises the demand for deep sleep our afternoon sleep is also likely to be dominated by REM sleep. Excessive amounts of REM sleep have been associated with depression and de-motivation and in the case of depression, pharmacological treatment results in a beneficial reduction in the amount of REM sleep.

Waking from the REM stage is the natural process of terminating the sleep cycle and waking in the REM state results in a greater feeling of re-freshness. REM deprivation has been shown to elevate exercise blood lactate on the following day and since higher lactates also result in higher levels of perceived exertion, a greater effort is required for the workout. While, consecutive nights of REM deprivation in rats has shown hyper-sexuality, increased aggression and in humans, impaired cognitive (brain) function.

In summary, to exploit the benefits of sleep on health and fitness, we must first assess what aspect of performance needs improving. When levels of motivation and mood are impaired, the amount of REM sleep may be excessive and reducing the amount of REM sleep can be easily achieved by limiting the amount of daytime sleep.

However, prior to maximal physical performance it is important to not be REM deprived, otherwise, the required effort for the performance is likely to be greater. It would also be beneficial to wake from the REM cycle, for both cognitive and physical morning performances. For maximising muscle recovery after training, the deep sleep time and growth hormone release can be optimised by taking a nap after high intensity sessions and by following consistent bedtimes.

Unfortunately, regardless of the good sleep hygiene practices, some people are unable to optimise their sleep patterns due to an underlying sleep disorder.

Sleep Respiratory Disorder, Health and Fitness.

It is estimated that a large portion of sleep disorders have gone undiagnosed in the general population. Although exercise has proved to be beneficial for some types of sleep disorders such as insomnia, most sleep disorders are more famous for having a negative effect on physical and mental performance. The most common form of sleep disorder is sleep apnoea and may affect up to 10% of the general population. The word "may" is used because it is believed many are living untreated with this condition, thinking it's just normal behaviour. This condition is most prevalent in the population of men over the age of 30 and is coupled with excessive day-time sleepiness and fatigue. The condition is caused by upper respiratory airway obstruction and many sufferers do not suspect this condition until they have been referred to a sleep specialist.

Respiratory infections, hay fever and other allergies all contribute to a less serious form of this disorder called increased upper airway resistance. Although snoring is a regular characteristic for the sleep of many people, it is also a symptom of increased upper airway resistance. Any form of upper airway resistance or obstruction can be responsible for a decrease in the amount of REM and deep sleep. This poor sleep quality will increase the levels of daytime fatigue and will slow down the muscle recovery process after strenuous physical efforts. Fortunately, both conditions of obstructive sleep apnoea and upper airway resistance can be treated. (If this sounds like you, please tell your doctor to refer you to a sleep/respiratory specialist.)

In the most serious case of obstructive sleep apnoea, a mask needs to be worn during sleep, to increase the air pressure in order to maintain the opening of the upper airway. In the less serious case of upper airway resistance, nasal sprays can be used over periods of respiratory infection or allergies. However caution should be taken in using certain nasal sprays as they are not designed for long-term use and can damage the nasal membrane. Sports competitors must also be certain that the sprays do not contain any banned substances such as pseudoephedrine.
Although sleep disorder sufferers are often skeptical about treatment and the processes involved, people who have been treated for sleep disorders can usually attest to becoming fitter and healthier individuals.

Tahnee Kinsman

Sleep Scientist
Australian Institute of Sport.

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