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 Post subject: Why sleep is important
 Post Posted: Sat Dec 17, 2005 5:14 pm 
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Why sleep is important

By Nisreen Officewala
@ TML / 14DEC2005

Sleep is a fundamental activity that consumes one-third of our lifetime and can overpower all other needs. But what does sleep do for us and why do our bodies instinctively devote so much time to it?

Sleep was always considered a period of dormancy. However, in 1953 scientists discovered Rapid Eye Movement (REM), a period of heightened cerebral activity in which the brain assimilates emotional experiences and new information acquired during waking hours. During REM a person also dreams. This discovery was significant because it helped create models to understand the physiology of sleep and pave the way for treating sleeping disorders. What happens to us while we sleep is still a mystery, the discovery was a catalyst in understanding the many benefits of sleep.

Human sleep occurs in cycles, each comprising five recurring stages: four non-REM stages and the REM stage. A sixth stage, waking, is also often included in sleep models.

The waking stage is referred to as relaxed wakefulness, because this is the stage in which the body prepares for sleep. As a person becomes sleepier, the body begins to slow down, muscles relax, and eye movement slows to a roll.

Stage 1

Sleep, or drowsiness, is when there is a 50% reduction in activity. The eyes are closed during sleep, but if aroused from it, a person may feel as if he or she has not slept. This stage may last 5 to 10 minutes.

Stage 2

Is a period of light sleep during which the heart rate slows, and body temperature decreases. At this point, the body prepares to enter deep sleep.

Stages 3 and 4

These are deep sleep stages, with Stage 4 being more intense than Stage 3. These stages are also known as slow-wave, or delta, sleep.

Stage 5,

REM sleep is distinguishable by the changes in ones physiological state, including its characteristic rapid eye movements. During the REM phase, in a normal sleep pattern, eyeballs move rapidly – though the eyes are closed, heart rate and respiration speed up and become erratic, while the face, fingers, and legs may twitch. Intense dreaming also occurs during REM sleep as a result of heightened cerebral activity. The body experiences simultaneous paralysis in major voluntary muscle groups.

It is generally thought that REM-associated muscle paralysis is meant to keep the body from acting out the dreams that occur during this intensely cerebral stage. The first period of REM typically lasts 10 minutes, with each recurring REM stage lengthening, and the final one lasting an hour.

The sleep cycle

Each sleep cycle ends after the completion of the REM stage. The first usually lasts for 100 minutes. Each subsequent cycle lasts longer, as its respective REM stage extends. It is recommended that an adult gets eight hours of sleep to go through five sleep cycles that is required for a person to wake up refreshed and energised.

The importance of sleep

Adequate sleep is crucial to proper brain function – no less than air, water, and food. When we sleep our bodies repair much of the muscle wear and tear from our daily routine. Further researchers believe that the brain assimilates new information and stores it into long term memory.

After periods of extended wakefulness, neurons may begin to malfunction, visibly affecting a person’s behaviour. Sleep deprivation also has an immediate impact on the cognitive abilities of a person. Any amount of sleep deprivation will diminish mental performance, cautions a professor of neurology at the University of Minnesota Medical School, Mark Mohowald.

"One complete night of sleep deprivation is as impairing in simulated driving tests as a legally intoxicating blood-alcohol level." It is also suggested that chronic sleep loss may not only hasten the onset but could also increase the severity of age-related ailments such as diabetes, hypertension, obesity, and memory loss.

Maintaining good sleep hygiene

Sleep quality is reflected by the proportions of time we spend in different stages of sleep throughout the night. 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 choose to practice our sleep habits and is a very important aspect of health and fitness. Consistent bedtimes and sleep duration are required in order to optimise sleep patterns. Delayed bedtimes or early awakenings that result in partial sleep deprivation can affect mental and physical performance the following day. Too much 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 need to spend in our deep sleep state. Individuals engaging in high intensity workouts can have up to three times the amount of deep sleep, representing 25-35% of the nights sleep. Since the growth hormone is facilitated by the neurophysiology of deep sleep it is important that such individuals do not compromise the first third of their nights sleep by delaying their normal bedtime or by sleeping in a potentially arousing environment.

Further waking from the REM stage is the natural process of terminating the sleep cycle and results in a greater feeling of re-freshness.

· The last third of the nights sleep and daytime napping is dominated by the REM sleep stage. Excessive amounts of REM sleep have been proven to be counter productive for those suffering from depression and de-motivation. When levels of motivation and mood are impaired, reducing the amount of REM sleep can be easily achieved by limiting the amount of daytime sleep.

In summary, to exploit the benefits of sleep on health and fitness, we must first assess what aspect of performance needs improving. Having established a pattern that helps us optimise performance we must follow it as a routine

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