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{{TNT|Segmented}}

{{TNT|Segmented}}

A [[biphasic]] [[Template:Polyphasic Sleep Schedules|schedule]]<ref>[https://www.polyphasic.net/schedules/biphasic/ polyphasic.net]. Retrieved 23-11-2020.</ref>, which contains two [[cores]] at night, usually with a high total sleep time, close to a personal [[monophasic]] baseline. While potentially not as popular as [[Siesta]] and [[E1]], it does promise several niches that completely set it apart from its Biphasic counterparts.

Segmented is a [[biphasic]] [[Template:Polyphasic Sleep Schedules|schedule]]<ref>[https://www.polyphasic.net/schedules/biphasic/ polyphasic.net]. Retrieved 23-11-2020.</ref> with two [[cores]] at night, usually with a total sleep time close to one's personal [[monophasic]] baseline.

==Origin==

==Origin==

Segmented sleep, sometimes referred to as Bifurcated sleep, is one of the oldest polyphasic schedules. Aside from its role as the progenitor of [[Dual core|Dual Core sleep]], its creation ('''non-reducing''') was natural and dated back to the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763365/ preindustrial era] (1750-1850), making it roughly 250 years old as of today. In short photoperiods (less daytime hours and more night time hours), it was researched that human sleep is also [https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2869.1992.tb00019.x naturally segmented]. What is commonly observed in this Segmented behavior is that people would often go to bed after sunset, wake up after some hours at night, stay awake for a couple hours, and then go back to bed until sunrise hours. Segmented sleep is still common nowadays, being involuntarily or voluntarily practiced by many in the world. Nowadays, '''naturally Segmented sleepers''' have a short wake gap between 2 cores (~1.5-3h) as a result of interrupted monophasic sleep, in the middle of the night. It only makes sense then, that sleepers would wake up feeling refreshed from the first core, do something at night, before they go back to sleep when sleepiness level rises enough.

Segmented sleep, sometimes referred to as bifurcated or divided sleep, is one of the original polyphasic sleep patterns. It is the basis of the [[Dual core]] schedule line. In its non-reducing form, it is believed to have been practiced by some human societies since time immemorial until the advent of electric lighting . In short photoperiods (fewer daylight hours), it has been shown that human sleep is naturally segmented<ref>https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2869.1992.tb00019.x</ref>.  

 

People would often go to bed some time after sunset, wake up after a few hours, stay awake for a couple hours, and then go back to bed until sunrise. Some naturally Segmented sleepers report interrupted monophasic sleep, where they wake up in the middle of the night. They are often suggested to adopt a Segmented sleep schedule.

==Mechanism==

==Mechanism==

Currently, the Polyphasic Discord Community has discovered more sleep mechanics regarding Segmented sleep. For starters, Segmented is one of the 5 schedules with '''only core sleeps''' (2) and '''no naps'''. It is also one of the 4 Biphasic schedules available. The entire basis of Segmented sleep is constructed based on the sleep peaks. It is widely regarded that the early hours of the night (~9-10 PM, '''SWS peak'''), when natural melatonin secretion is kickstarted, quality SWS will largely benefit if sleep time begins around these hours. Throughout a lot of EEG readings of adapted sleepers, it is commonly seen that the first core sleep is highly SWS-oriented, while the second core sleep, being near sunrise hours (~6-9 AM, '''REM peak'''), has a strong propensity for densely populated REM sleep. However, on Segmented it is worth noting that some minor amount of REM sleep can still be present in the first core sleep, and the same for SWS in the second core. The segmentation of the main monophasic core sleep into 2 core sleeps that align with the sleep peaks bolster the sleep quality with much deeper core sleeps, and allow for <u>some potential sleep reduction</u> with strict bedtime everyday. Since 2 core sleeps are already allocated to night hours (which is similar to monophasic sleep's distribution of sleep), no naps in the day are needed, because the amount of light sleep from both cores is sufficient to sustain wakefulness for the entire day.

The [[Polyphasic Discord|Polyphasic Discord Community]] has discovered some possible mechanics of Segmented sleep. The basis of Segmented sleep is the sleep peaks. During the early hours of the night (~21-24), when natural melatonin secretion starts, SWS can be gained efficiently. In EEG readings of adapted sleepers, the first core sleep is usually dense in SWS, whereas the second core sleep contains  primarily REM sleep. The divided core sleeps are thus denser in vital sleep stages, and allow for a small cut in total sleep with stable sleep times. Naps in the day are not needed because the amount of light sleep cut is small enough, and the day gap is also substantially shortened compared to a monophasic schedule.

 

Both core sleeps are scheduled to be 3.5 hours by default because the sleep cycles are known to lengthen to about 105 minutes from the approximately 90-minute cycles on monophasic sleep. This would also explain the viability of the schedule despite having fewer cycles.

Even though it may look odd that both core sleeps last for 3.5h rather than the would-be 3h, or 4.5h, it was later explained that each core consists of 2 full sleep cycles plus an extra 30 minutes of sleep time to cover the '''statistically likely REM period''' (just like 5h and 6.5h core). The statistically likely REM period originates from ''Polyphasic Society'', and the evidence for it is very poor (eight monophasic readings). While its existence is questionable, it is still possible to see the effects from having the cores be 3.5 hours long. Another explanation for the 30m extension on each core is from the possibility that the cycles extend to roughly '''105m''' as compared to the standard 90m cycles in monophasic sleep. This would explain the viability of the schedule despite having fewer cycles.

The wake gap between each core should at least 90 minutes, with a longer gap recommended (~2.5-3 hours) for non-natural Segmented sleepers. The reason for this is to prevent the cores from becoming interrupted sleep, in which there is a only a brief period of awakening during sleep, before the sleeper goes back to sleep, which disrupts the sleep cycle and drastically reduces sleep quality.  

The wake gap between each core should be '''at least 90m''', and even more (~2.5-3h) for non-natural Segmented sleepers to ease the adaptation. The first thing is to avoid the interrupted sleep issue. Interrupted monophasic sleep often occurs when there is a only a brief period of awakening during sleep, before the sleeper goes back to sleep. Staying awake for at least ~90m will separate the interruption and create an entirely '''new sleep architecture for the second core'''. Should the wake gap be too short, it will be unproductive to do different activities and it may be difficult to fall asleep in the second core as sleep pressure is not high enough to induce sleep. Some people have quit Segmented with a 2h gap because of the inability to adapt or feeling too unproductive during these short night gap.

Staying awake for at least ~90m will usually prevent this, so that the second core starts in a new sleep cycle. A wake gap that is too short is unlikely to be productive time, and it may also be difficult to fall asleep as not enough sleep pressure has been accumulated. The original default recommendation was 2 hours of gap, but has since been changed to 3 hours as some people were unable to fully adapt to the 2-hour gap version.

== Adaptation==

== Adaptation==

Before attempting this schedule, it is important to look over all Biphasic patterns to choose if Segmented sleep is worth the choice. For naturally Segmented sleepers, the adaptation is basically complete if they already have a long exposure to the core-split mechanics. For non-natural Segmented sleepers, adapting to Segmented is potentially more challenging than to a biphasic pattern with a long, uninterrupted core sleep at night, such as Siesta and E1. It is still possible to adapt to Segmented, but initially waking up from the first core can pose common issues (e.g, heavy sleep inertia, boredom during the night gap). The second core sleep, being replete with REM sleep, can cause certain amounts of sleep inertia, grogginess or even slight dizziness upon waking up, due to the effects of the dense eye-movement activities from REM sleep. Over time, with enough consistency, these issues will no longer persist, and waking up will be invigorating from each sleep. However, compared to naturally Segmented sleepers, there can still be certain glimpses of mild unproductivity during the night gap after adaptation, and it may require '''an extended amount of time on the schedule''' to fully enjoy the night gap.

For naturally Segmented sleepers, the adaptation is easy if they already have a long exposure to the core-split mechanics. For non-natural Segmented sleepers, adapting to Segmented is potentially more challenging than to a biphasic pattern with a long, uninterrupted core sleep at night, such as Siesta and E1. It is still possible to adapt to Segmented, but initially waking up from the first core can pose common issues (e.g, heavy sleep inertia, boredom during the night gap). The second core sleep, being replete with REM sleep, can cause certain amounts of sleep inertia, grogginess or even slight dizziness upon waking up, due to the effects of the dense eye-movement activities from REM sleep. Over time, with enough consistency, these issues will no longer persist, and waking up will be invigorating from each sleep. However, compared to naturally Segmented sleepers, there can still be certain glimpses of mild unproductivity during the night gap after adaptation, and it may require '''an extended amount of time on the schedule''' to fully enjoy the night gap.

Once Segmented is adapted to, one then then proceed to a Dual Core, or even Triphasic schedule, following the habit of segmenting the main night sleep into 2 smaller core sleeps.

Once Segmented is adapted to, one then then proceed to a Dual Core, or even Triphasic schedule, following the habit of segmenting the main night sleep into 2 smaller core sleeps.