Changes

==Circadian rhythm==

==Circadian rhythm==

The circadian rhythm is the body clock aligned to local solar time by light exposure, among other factors. It produces hormonal effects that changes throughout the day consistently to produce effects on the body. One of the main effects is the secretion of melatonin, the presence of which is essential for entering SWS, and also affects the timing of REM sleep.

The circadian rhythm is the body clock aligned to local solar time by light exposure and food intake, among other factors. It generates hormonal changes throughout the day consistently to produce effects on the body. One of the main effects is the secretion of [[Wikipedia:Melatonin|melatonin]], the presence of which is essential for entering SWS, and also affects the timing of REM sleep.

After sunset when light levels reduce, the body starts to secrete melatonin to promote sleep. The rising levels of melatonin early in the night allows the body to gain SWS in the first few sleep cycles. In contrast, as melatonin levels drops in the morning, REM becomes the preferred sleep phase to be gained.

After sunset when light levels reduce, the body starts to secrete melatonin to promote sleep. The rising levels of melatonin early in the night allows the body to gain SWS in the first few sleep cycles. In contrast, as melatonin levels drops in the morning, REM becomes the preferred sleep phase to be gained.

[[File:Melanopic.png|thumb|Melanopic sensitivity function]]

[[File:Melanopic.png|thumb|Melanopic sensitivity function]]

In modern times with the advent of artificial light, many people's circadian rhythms have been pushed forward (i.e. later). However, this exposure to artificial light sources also compromises people's ability to gain SWS efficiently. The extent to which light influences the circadian rhythm is given by the melanopic sensitivity function, which peaks at ~480nm (blue) and drops off on both sides. To reduce this effect, a [[dark period]] must be employed, during which blue and green lights must not enter the eye. This can be done in many ways, such as with [[red goggles]] or [[screen filters]].

In modern times with the advent of artificial light, many people's circadian rhythms have been pushed forward (i.e. later). However, this exposure to artificial light sources also compromises people's ability to gain SWS efficiently. The extent to which light influences the circadian rhythm is given by the melanopic light sensitivity function, which peaks at ~480nm (blue) and drops off on both sides. To reduce this effect, a [[dark period]] must be employed, during which blue and green lights must not enter the eye. This can be done in many ways, such as with [[red goggles]] or [[screen filters]].

To maintain the stability of the circadian rhythm, all polyphasic sleep schedules must stay relatively consistent day-to-day, without large changes in core or dark-period timings. As such, schedules that are not aligned with the 24-hour day are unsustainable and unhealthy.

To maintain the stability of the circadian rhythm, all polyphasic sleep schedules must stay relatively consistent day-to-day, without large changes in core or dark period timings. As such, schedules that are not aligned with the 24-hour day are unsustainable and unhealthy. Examples of which includes cycles longer than 24 hours (delaying sleep phases continually) or employing drastically different sleep schedules on a day-to-day basis.

==Minimum sleep threshold==

==Minimum sleep threshold==

Since vital sleep stages are generally not possible to reduce, the amount of compression required to sustain a schedule increases dramatically as total sleep time reduces. Compressing sleep, however, requires adaptation, and greater levels of compression necessitates harsher and/or longer adaptations. As such, schedules can be classified by their difficulty level, which is mostly a function of the amount of sleep cut.  

Since vital sleep stages are generally not possible to reduce, the extent of compression required to sustain a schedule increases dramatically as total sleep time reduces. Compressing sleep, however, requires adaptation, and greater levels of compression necessitates harsher and/or longer adaptations. As such, schedules can be classified by their difficulty level, which is mostly a function of the amount of sleep cut.  

It is worth noting that younger individuals whose brains and bodies are still developing will need more SWS and REM than adults, which increases their minimum sleep thresholds and makes reducing sleep more difficult. In addition, it has been suggested that NREM2 might have other functions in the development of the brain, and thus cutting it could be potentially problematic.  

It is worth noting that younger individuals whose brains and bodies are still developing will need more SWS and REM than adults, which increases their minimum sleep thresholds and makes reducing sleep more difficult. In addition, it has been suggested that NREM2 might have other functions in the development of the brain, and thus cutting it could be potentially problematic.  

|7-8

|7-8

|<1 hour

|<1 hour

|

|Recommended for beginners or those needing significant flexibility.

|-

|-

|Moderate

|Moderate

|5-6

|5-6

|1-2 hours

|1-2 hours

|

|Require a significant adaptation process, but can be quite flexible after adapting.

|-

|-

|Hard

|Hard

|E3, DC2, Triphasic

|E3, DC2

|4-5

|4-5

|2-3 hours

|2-3 hours

|

|Require harsh adaptations and are not particularly flexible for most people.

|-

|-

|Very hard

|Very hard

|DC3, Bimaxion

|DC3, Bimaxion, Triphasic

|4

|4-5

|3-4 hours

|2-3 hours

|These schedules are harder than the "Hard" ones because they do not contain a longer core during SWS peak hours.

|Considered harder than the "Hard" ones because they do not contain a longer core during SWS peak hours.

|-

|-

|Extremely hard

|Extremely hard

|<4

|<4

|>4 hours

|>4 hours

|

|Not considered possible for most people.

|}

|}

==Sleep block lengths==

==Sleep block lengths==

Sleeps on polyphasic schedules are broadly characterized as [[cores]] and [[naps]].  

Sleeps on polyphasic schedules are broadly categorised into [[cores]] and [[naps]].  

Cores are long blocks of sleep that contain at least one full sleep cycle. They are typically scheduled to be a multiple of a 90 minutes, which is a common sleep cycle length. However, alternative core lengths can be done to either to plan for alternative cycle lengths or in an effort to gain extra time in SWS or REM. Cores are generally considered to be essential, because they provide the necessary amount of SWS to sustain life. As such, schedules without cores (i.e. [[Nap only|nap only schedules]]) have extremely low success rates.  

Cores are long blocks of sleep that contain at least one full sleep cycle. They are typically scheduled to be a multiple of a 90 minutes, which is a common [[Wikipedia:sleep cycle|sleep cycle]] length. However, alternative core lengths can be done to either to plan for alternative cycle lengths or in an effort to gain extra time in SWS or REM. Cores are generally considered to be essential, because they provide the necessary amount of SWS to sustain life. As such, schedules without cores (i.e. [[Nap only|nap only schedules]]) have extremely low success rates.  

Naps are short blocks of sleep, typically about 20 minutes on default schedules. Naps allow for a small amount of REM to be gained. Moreover, naps help sleepers sustain wakefulness through gaps. Longer up to (~45 minute) naps can be used in during the REM peak around dawn to gain even more time in REM. Longer naps in other times of the day can lead to SWS wakes, which can be exceptionally difficult to wake from for some people, especially during periods of high SWS deficit.  

Naps are short blocks of sleep, typically about 20 minutes on default schedules. Naps allow for a small amount of REM to be gained. Moreover, naps help sleepers sustain wakefulness through gaps. Longer naps (up to ~45 minutes, known as [[pronap]]<nowiki/>s) can be used in during the REM peak around dawn to gain even more time in REM. Longer naps in other times of the day can lead to SWS wakes, which can be exceptionally difficult to wake from for some people, especially during periods of high SWS deficit.  

Core sleeps are favoured during night time, as they allow sufficient time to complete SWS-filled sleep cycles. They are also easier to schedule at night for most people due to social obligations. Naps are favoured in the day, since deeper sleep stages are less likely to appear then. After adaptation, naps can be relatively flexible, whereas cores are much harder to move.

Core sleeps are favoured during night time, as they allow sufficient time to complete SWS-filled sleep cycles. They are also easier to schedule at night for most people due to social obligations. Naps are favoured in the day, since deeper sleep stages are less likely to appear then. After adaptation, naps can be relatively flexible, whereas cores are much harder to move.

==Consistency==

==Consistency==

During adaptation, most polyphasic schedules (other than non-reducing ones) are strict, that is, they must be done very consistently, without missed sleeps, moved sleeps, oversleeps, or undersleeps. If your life schedule cannot accomodate the sleep schedule you are planning for almost all days, it is unlikely that you will ever be able to adapt to it. One or two minor mishaps should not cause too much damage to your adaptation. However, as the mistakes accumulate, your chance of adaptation decreases. It is therefore necessary to plan ahead and avoid these mistakes, by carefully scheduling your life around the sleeps as well as setting proper alarms to avoid oversleeps.

During adaptation, most polyphasic schedules (other than non-reducing ones) are strict, that is, they must be done very consistently, without missed sleeps, moved sleeps, oversleeps, or undersleeps. If your life schedule cannot accomodate the sleep schedule you are planning for almost all days, it is unlikely that you will ever be able to adapt to it. One or two minor mishaps should not cause too much damage to your adaptation. However, as the mistakes accumulate, your chance of successful adaptation decreases. It is therefore necessary to plan ahead and avoid these mistakes, by carefully scheduling your life around the sleeps as well as setting proper alarms to avoid oversleeps.

==Schedule lines==

==Schedule lines==