What is sleep?

article047My interest in sleep initially stemmed from my ability to sleep anytime and anywhere and then later from AR – particularly with regard to sleep cycles, duration and deprivation. AR-induced sleep deprivation is of special interest because in events it is easy to observe how each person responds differently, some having higher levels of tolerance than others. Cognitive impairment, hallucinations, reduced physical performance, compromised immune responses and increased susceptibility to heatstroke are characteristic of this state.

But, sleep deprivation is not isolated to the race environment. It’s an abnormal turned normal state in our “burning-the-candle-at-both-ends” society.

Sleep has been stereotyped as a state in which the brain is turned off and the body rests, allowing for recovery from the vigour’s of wakefulness. Research in the last decade or so has proved that sleep is an active phase in which the brain reaches peak activity during some phases. It is a highly organised and active state, divided into cycles, which comprise 5 distinct stages.

Animal studies have shown that sleep is necessary for survival. Take rats for example; they normally live to 2-3 years. But, when deprived of sleep, they only live for about 3 weeks. In addition they develop abnormally low body temperatures and sores on their tail and paws – probably because their immune system is compromised. Rat studies also demonstrated that nerve signalling patterns generated during the day were repeated during deep sleep. Thus, this pattern repetition may help encode memories and improve learning.

Sleep is necessary for the proper functioning of the nervous system. Too little sleep leaves us drowsy and unable to concentrate the next day. In children, growth hormone is released during sleep and in adults, cells increase production of proteins, the building blocks needed for the growth and repair of tissues from damage due to stress, exercise, chemicals, UV-light etc.

A polysomnogram is a test of sleep cycles and stages through the use of continuous recordings of brain waves (Electroencephalogram; EEG), muscular electrical activity (Electromusculogram; EMG) and eye movement (Electrooculogram; EOG). Accordingly, electrodes are placed on the scalp (EEG), outer edge of eyelids (EOG) and chin (EMG). Respiratory rate, blood pressure, blood oxygen levels, heart rate and direct observations of the person during sleep may also be recorded.

No caffeinated drinks, alcohol or medication are allowed before the test. Abnormal results indicate a sleep disorder – insomnia (when you can’t sleep), sleep apnea (when you stop breathing while you’re asleep), narcolepsy (when you keep falling asleep even while eating or having a conversation), breathing difficulties or behavioural abnormalities.

A night of sleep consists of a number of sleep cycles, each lasting 90-110 minutes. Each cycle is made up of 4 stages and the dreaming stage in which rapid eye movements (REMs) are noted. Stages 1 and 2 are relatively light phases while stages 3 and 4 constitute “deep sleep”. The duration of stages 3 and 4 are increased in athletes and sleep deprived people and are believed to be the most beneficial stages, a time in which the body recovers from fatigue, repairs muscles and cells and replenishes its energy.

Circadian rhythms are regular changes in mental and physical characteristics (blood pressure, body temperature, hormone levels etc) during the course of a day, often referred to as a “biological clock”. This clock is in fact a pair of pinhead-sized structures called the suprachiasmatic nucleus (SCN) found in the hypothalamus of the brain, just above where the optic nerves cross.

Light that reaches photoreceptors in the retina of the eye (back of the eye) creates signals that travel along the optic nerve to the SCN. Signals from the SCN go to various brain regions, including the pineal gland, which responds to light-induced signals by switching off the production of the hormone melatonin. Thus, the body’s levels of melatonin increases after dark, making you feel drowsy.

By depriving people of time cues like light and dark, scientists found that the body works on a 25hr cycle, not 24hr. But, sunlight and other signals reset the SCN, thus we follow a 24hr cycle of the sun. Circadian rhythms are also affected by external time cues, like alarm clocks, noise (garbage truck; birds) and artificial lights.

Thus, travel (where you cross time zones) and shiftwork are circadian rhythm disruptions that leave you feeling tired, listless and unable to fall asleep at night or when you lie down. The duration and severity of jet lag depends on the number of time zones crossed and the direction of travel (worse going East to West).

Interestingly, people with total blindness often experience life-long sleeping problems because their retinas are unable to detect light. They have a kind of permanent jet-lag as their circadian rhythm follows their innate 25hr cycle.

The amount of sleep you need each night depends on many factors including age. Infants require about 16hrs, teenagers about 9hrs on average. For most adults 7-8hrs a night is sufficient. But, some may need as few as 5hrs, others as much as 10hrs. You will obviously need more if you’ve been sleep deprived.

With regards to sleep deprivation, there are three commonly asked questions:

  • Do you fall asleep within 5 minutes of your head hitting the pillow?
  • Do you feel drowsy during the day, particularly during boring activities?
  • Do you struggle to wake up?If you’ve answered Yes to any of these, there’s a good chance that you’re sleep deprived, and the reason in most cases probably relates to lifestyle – how much we work, what we eat and drink and how much sleep we “allow” ourselves each night.

    My point here is that even though you’re getting 6 or 7hrs a night, you may have an innate need for 9hrs, of sleep. Thus, you’re perpetually sleep deprived.

    The widespread practise of “burning the candle at both ends” in western societies has created so much sleep deprivation that what is really abnormal sleepiness is almost the norm. Getting too little sleep creates a sleep debt that will have to be repaid at some stage. And, while we can’t adapt to getting less sleep than we need we can get used to a sleep-depriving schedule. But, judgement, reaction time, cognitive functions and physical performance are impaired.

    This relates to lifestyle and the development of good sleep habits.


    • Relax your body before sleep – warm bath or meditation. Unwind by listening to music or reading before sleep
    • Avoid caffeinated drinks and drugs (diet pills and decongestants). They stimulate parts of the brain so you’ll battle to fall asleep and will cause you to wake up during the night
    • Avoid nicotine. Like caffeine, nicotine is a stimulant that extends the time it will take you to fall asleep and you’re likely to wake up after 3-4 hours due to nicotine withdrawal.
    • Avoid alcohol. While it will help you to fall quickly into a light sleep, alcohol restricts the REM stage and the deeper, resorative stages 3 and 4.
    • Don’t nap in the afternoon if you battle to sleep at night
    • Exercise regularly, but make certain it is at least 2-3hrs before bedtime. Elevated body temperatures delay sleep onset.
    • Establish a regular routine – wake up and go to sleep same time each day, including weekends
    • Reduce the stress and anxiety in your life
    • Before bed make a list of things to do the next day so you don’t worry about things to remember before going to sleep
    • Avoid exposure to bright lights before bedtime
    • Don’t work in your bedroom. Ensure that your sleep environment is comfortable, quiet, dark and at a comfortable temperature.
    • If you can’t sleep, don’t toss in bed. Get up and do a relaxing activity (read, listen to music), then try again to sleep. Clear your mind and don’t solve the day’s troubles.
    • Pets can disturb your sleep. Put them on the floor or in another room if they keep waking you up.
    • Address your partners problems – snoring, tossing and turning, getting up to go to the loo, sleep talking – which may be affecting your quality of sleep

    I’ve always maintained that you should go into a race well rested as sleep cannot be banked. If your sleep levels are saturated, you’ll be better able to handle the little or no sleep situation in AR, will be less likely to get ill after the event and will recover far faster from sleep deficit after the event.

  • Author: Lisa de Speville