Polyphasic sleep refers to the practice of sleeping multiple times in a 24-hour period, in contrast to monophasic sleep (once per day). It usually results in more total time being awake by lowering the total amount of sleep needed. It does not imply any particular sleep schedule. The circadian rhythm disorder known as irregular sleep-wake syndrome is an example of polyphasic sleep in humans, although in most cases, polyphasic sleep is not a disorder, but rather a choice. People like the fact that they can get more things done in the extra hours gained by following a polyphasic sleep pattern, without feeling sleep deprived.
The military is interested in this type of napping, since soldiers may not be able to achieve the recommended eight hours of sleep per day. The result is increased vigilance compared to the case of a single “block” of sleep of the same total duration.
Literature strongly suggests that shorter, polyphasically-placed sleep is the rule, rather than the exception, across the entire animal kingdom. Humans have adopted monophasic sleep only because the rules of society impose it. Also, a few hundered years ago, when electricity was not available (there was light for only 10 hours, instead of 16 nowadays), people used to sleep a few hours a night, wake up for 2-3 hours, and then go back to sleep.
A variation of polyphasic sleep is freestyle sleep, when the person falls asleep whenever sleepy and wakes up whenever rested, without regard to the time of the day, the time between sleeping periods or the number of sleeping periods (no alarm clock is used). This type of sleep leads to maximum mental performance.
The 5 most mentioned types of polyphasic sleep (if we include monophasic sleep too) are summarized in the image below. Typically, you will need an alarm clock in order to achieve this, otherwise you will oversleep and loose your discipline.
The Uberman cycle consists of 20 to 30 minute naps every 4 hours, resulting in 6 naps each day. The Uberman cycle is highly efficient, and usually results in extremely vivid dreams as the brain goes directly into REM sleep, and in feeling healthy and refreshed upon waking.
The Everyman cycle has one longer “core” nap (1.5 hours) that is supplemented with several 20-30 minute naps. It allows more flexibility in nap times and results in 3-4 hours of sleep per day.
The Biphasic cycle consists of sleeping for 4-4.5 hours at night, and then taking a 90 minute nap around noon (like most students nowadays do).
People that experiment with polyphasic sleep of 2-3 hours a day in 24 hours, can have a slightly lowered performance and mood and increased sleep pressure when trying to get up. Since they tend to have mainly REM sleep during the naps, NREM waves sometimes occur during the awake periods. They may also gain more weight compared to monophasic sleepers. Occasional sleep bonuses, when for one day the person is allowed to sleep as much as he wants, can lead to a significant boost in performance and mood.
