Sleep Amounts: 6 hours is not enough
There is no single normal amount of sleep. Each person has a genetically determined amount of sleep that must be obtained to be normally alert. It has been theorized that there is a minimum amount, termed core sleep, that is essential for basic function. Perhaps 4 to 5 hours in duration and dominated by slow wave sleep, this may be sufficient to prevent death or psychosis, but is clearly inadequate for normal vigilance, safety and health. The range of sleep thought necessary for optimum health in most adults is between 7 and 9 hours. Chronic sleep durations below 4 hours and above 10 hours are associated with significantly reduced health.
There are scientific means of determining what an individual’s requirement is, but these are complex and impractical outside of a research setting. A reasonable method for making your own such determination is to figure out how much sleep allows you to feel awake throughout the day without struggling to remain so, even when engaged in quiet sedentary activity. You will most likely find that this requires more sleep per night than you previously thought.
An adequate sleep quantity should provide you with the alertness sufficient to operate at peak efficiency. Humans obviously can function relatively acceptably at sub optimal sleep levels. But even modest sleep reduction causes the build-up of what has come to be called a sleep debt - one which must be paid one way or the other - either by an increase in sleep or with impaired function, potentially dangerously so. Sleep amounts below 5 hours are of particular concern; people at these levels showing rather dramatic levels of sleep deprivation induced impairment. New research on “recuperative sleep” used to make up for prior sleep loss suggests that approximately 9 hours or more are needed on a nightly basis to best recover from sleep deprivation or restriction.
Movement during Sleep
You are not paralyzed during sleep - well, not most of the night.
Muscle tone and physical activity progressively decrease across the sleep cycle. As discussed above, there is a complete loss of muscle tone during REM sleep. However, random brief twitches are common, even in REM sleep. There is significant physical activity even in normal sleep. Virtually everyone has experienced a brief jerk as they drift into sleep. These are termed sleep starts or hypnic jerks, and are entirely normal. Major adjustments in body positioning occur at least once to twice per hour. Smaller or fine movements, such as a finger or foot, often produce momentary arousals (brief breaks in the normal continuity of sleep) and can be perfectly normal at 10 or so times per hour of sleep. Even people who say they don’t move all make these same adjustments; they simply aren’t encoded in memory. In fact, if the rate and amount of movement drops below normal, a person can wake in the morning feeling stiff or aching.
If you seem to exhibit a great deal of movement during your sleep, then you should explore the possibility that you may have an actual sleep disorder.
