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{{TNT|Segmented}}

{{TNT|Segmented}}

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

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 sleep, sometimes referred to as Bifurcated sleep, is one of the earliest polyphasic schedules. It is also one of the 4 Biphasic schedules available. Aside from its role as the progenitor of 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.

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'''. 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.

 

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.

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.

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 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.

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.

==Adaptation Difficulty==

 

== 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.

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.

Thus, the difficulty level of Segmented varies across individuals, and depends on the amount of sleep being scheduled. Overall, it is still considered a friendly schedule to begin sleeping polyphasically, as total sleep is among the highest of all schedules. While potentially not as popular as Siesta and E1, it does promise several niches that completely set it apart from its Biphasic counterparts. This will be discussed in the Lifestyle Considerations section.

The difficulty level of Segmented varies across individuals, and depends on the amount of sleep being scheduled. Overall, it is still considered a friendly schedule to begin sleeping polyphasically, as total sleep is among the highest of all schedules.  

==Alternate Variants==

==Alternate Variants==

While the standard 3.5-3.5 core combination has brought about a lot of successes in the community, multiple other core combinations are also viable and have been succeeded on their own right. With proper consideration, polyphasic beginners can attempt these variants, with some precautions and recommendations at hand.

While the standard 3.5-3.5 core combination has brought about a lot of successes in the community, multiple other core combinations are also viable and have been succeeded on their own right. With proper consideration, polyphasic beginners can attempt these variants, with some precautions and recommendations at hand.

===Slightly shortened core sleeps===

 

=== Slightly shortened core sleeps===

<gallery mode="packed-overlay" widths="200" heights="200">

<gallery mode="packed-overlay" widths="200" heights="200">

File:Segmented short 1.png|Segmented with 6h total sleep (Version 1)

File:Segmented short 1.png|Segmented with 6h total sleep (Version 1)

The difference between 4.5-1.5 and 3-3 core distribution is that those with more SWS requirements can attempt the former option, while those with more REM sleep and a reasonable amount of SWS requirements can pick the latter. Overall, the 3-3 variant gives a better balance for each sleep stage, and has some slight advantage in adaptation success compared to the other variant. Both of these variants, however, follow the 90m -cycle rule in scheduling.

The difference between 4.5-1.5 and 3-3 core distribution is that those with more SWS requirements can attempt the former option, while those with more REM sleep and a reasonable amount of SWS requirements can pick the latter. Overall, the 3-3 variant gives a better balance for each sleep stage, and has some slight advantage in adaptation success compared to the other variant. Both of these variants, however, follow the 90m -cycle rule in scheduling.

===Uneven core durations===

===Uneven core durations===

[[File:Segmented Uneven.png|center|thumb|A Segmented variant with uneven core lengths]]This is one of the many variants whose core durations are not equal to each other. Excluding the 4.5-1.5 variant from the previous section, here either core can be '''slightly longer or shorter than the other''', and total sleep hovers around ~'''6.5-7h'''. The advantage of these variants is to salvage a bit more extra wake time than the original version, while essentially not increasing the adaptation difficulty by a lot. There is very '''rare''' success with these types of scheduling, however. Other viable combinations include <u>3-3.5</u>, or even <u>4.5-2.5</u> and <u>5-1.5</u>. It would be helpful to know the SWS and REM requirements before picking any of these variants, though.

[[File:Segmented Uneven.png|center|thumb|A Segmented variant with uneven core lengths]]This is one of the many variants whose core durations are not equal to each other. Excluding the 4.5-1.5 variant from the previous section, here either core can be '''slightly longer or shorter than the other''', and total sleep hovers around ~'''6.5-7h'''. The advantage of these variants is to salvage a bit more extra wake time than the original version, while essentially not increasing the adaptation difficulty by a lot. There is very '''rare''' success with these types of scheduling, however. Other viable combinations include <u>3-3.5</u>, or even <u>4.5-2.5</u> and <u>5-1.5</u>. It would be helpful to know the SWS and REM requirements before picking any of these variants, though.

Generally, variants with a longer first core can help with '''sustaining alertness better''' through the graveyard hours between 2 cores, and the second core does not need to be as long. However, the longer the first core, the less distinct its sleep architecture will become. What this means is that a longer first core (e.g, 4.5-5h core) will contain more REM sleep alongside the abundant SWS, and the second core will contain a less percentage of REM sleep. The longer first core also gives the impression of Siesta sleep, with the second sleep looking like a daytime core sleep.

Generally, variants with a longer first core can help with '''sustaining alertness better''' through the graveyard hours between 2 cores, and the second core does not need to be as long. However, the longer the first core, the less distinct its sleep architecture will become. What this means is that a longer first core (e.g, 4.5-5h core) will contain more REM sleep alongside the abundant SWS, and the second core will contain a less percentage of REM sleep. The longer first core also gives the impression of Siesta sleep, with the second sleep looking like a daytime core sleep.

===Late first core===

===Late first core===

[[File:Segmented Late First Core.png|center|thumb|Segmented with a late first core]]Even though it is initially deemed unrealistic and even impossible to schedule this segmented variant, over the years there have been a success or two. Sleepers who would schedule this variant are expected to have low SWS needs, and/or a lot of polyphasic experience as well as the stringent management of food, exercise and lighting. Since the first core is shifted out of the SWS peak entirely, it is necessary to employ various methods to ensure a sufficient amount of SWS, especially when coupled with heavy exercising. Similar to the previous options, multiple core combinations can be applied in this scheduling scheme.

[[File:Segmented Late First Core.png|center|thumb|Segmented with a late first core]]Even though it is initially deemed unrealistic and even impossible to schedule this segmented variant, over the years there have been a success or two. Sleepers who would schedule this variant are expected to have low SWS needs, and/or a lot of polyphasic experience as well as the stringent management of food, exercise and lighting. Since the first core is shifted out of the SWS peak entirely, it is necessary to employ various methods to ensure a sufficient amount of SWS, especially when coupled with heavy exercising. Similar to the previous options, multiple core combinations can be applied in this scheduling scheme.

There are, however, a lot of hefty benefits from this type of variant. For one, '''social time in the evening''' is secured, because sleep time is not as early as the standard version. For another, the '''wake gap between 2 cores can be smaller''' than the original version, because of a potentially higher SWS pressure that will be resolved in the second core sleep. This setup would also benefit those who can wake up at later hours in the evening with a shifted work schedule to late morning or later. A somewhat short sleeper would even benefit from this variant more - not only is sleep time reduced somewhat, but all the access to evening events like other monophasic individuals and an uninterrupted flow of daytime commitments, without needing any naps. Adaptation to this variant is expected to be very difficult, which is one important note to bear in mind.

There are, however, a lot of hefty benefits from this type of variant. For one, '''social time in the evening''' is secured, because sleep time is not as early as the standard version. For another, the '''wake gap between 2 cores can be smaller''' than the original version, because of a potentially higher SWS pressure that will be resolved in the second core sleep. This setup would also benefit those who can wake up at later hours in the evening with a shifted work schedule to late morning or later. A somewhat short sleeper would even benefit from this variant more - not only is sleep time reduced somewhat, but all the access to evening events like other monophasic individuals and an uninterrupted flow of daytime commitments, without needing any naps. Adaptation to this variant is expected to be very difficult, which is one important note to bear in mind.

{{TNT|Segmented-ext}}

{{TNT|Segmented-ext}}

===Extended/Non-reducing===

===Extended/Non-reducing===

The slight difference between Segmented-extended and non-reducing Segmented is that the former can still contribute to some amount of sleep reduction (e.g, 9h monophasic sleeper), while the latter does not reduce any sleep (e.g, 4.5-4.5 core combo for 9h sleeper). Either variants, however, only report some success over the years. The '''non-reducing''' variant has achieved a lot of success since the preindustrial era, which brings up the point that segmented sleep can be a natural sleep pattern for humans. Nowadays, with the advent of blue light and certain difficulties in managing the schedule alongside social time and hassling evening hours, it is deemed a lot harder to adapt to either variant. Another downside of both variants is that the longer core sleeps plus the wake gap between 2 cores makes the second core end later than usual. This can then clash with morning commitments if one has to wake up earlier than expected.

The slight difference between Segmented-extended and non-reducing Segmented is that the former can still contribute to some amount of sleep reduction (e.g, 9h monophasic sleeper), while the latter does not reduce any sleep (e.g, 4.5-4.5 core combo for 9h sleeper). Either variants, however, only report some success over the years. The '''non-reducing''' variant has achieved a lot of success since the preindustrial era, which brings up the point that segmented sleep can be a natural sleep pattern for humans. Nowadays, with the advent of blue light and certain difficulties in managing the schedule alongside social time and hassling evening hours, it is deemed a lot harder to adapt to either variant. Another downside of both variants is that the longer core sleeps plus the wake gap between 2 cores makes the second core end later than usual. This can then clash with morning commitments if one has to wake up earlier than expected.

The main concern is that since it is impossible for an average sleeper with at least 90m SWS to meet all SWS in the first core, the second core will have to provide the remaining SWS, and pushing the second core to very late hours at night may increase the difficulty of the process. Sleepers with lower SWS requirements or want to sleep less around evening hours can attempt this variant. However, as with a very unorthodox scheduling and the excessively long dark period, it will be tricky to make this Segmented variant work. This variant also takes away most, if not all social time in the evening; social time will have to be traded with the long wake gap between cores depending on personal preference.[[File:Siesta-hybrid.png|center|thumb|Segmented-Siesta hybrid]]Alternatively, Segmented can be scheduled with one core at night and one core in the day. Only a success or two have been reported thus far. This variant looks like Siesta with a long daytime core, and both core sleeps miss out on the peaks. The dark period should be 2-3h before the night core, and continue for ~2h after this core to stabilize the circadian rhythm. Adaptations are rare and a lot more difficult than a regular Segmented schedule, because '''skipping both sleep peaks can greatly hinder quality sleep'''. Over the course of adaptation, staying awake during the graveyard and morning hours will be tough, and having a long sleep in the day immediately can shake up the current sleep habits, if they are very different from this scheduling (e.g, regular 7-8h monophasic exclusively at night, non-nappers). The personal sleep peaks may change with artificial melatonin onset as a result of this new Segmented habits, however this entrainment will likely require an extended period of time for the circadian rhythm to be completely rotated.

The main concern is that since it is impossible for an average sleeper with at least 90m SWS to meet all SWS in the first core, the second core will have to provide the remaining SWS, and pushing the second core to very late hours at night may increase the difficulty of the process. Sleepers with lower SWS requirements or want to sleep less around evening hours can attempt this variant. However, as with a very unorthodox scheduling and the excessively long dark period, it will be tricky to make this Segmented variant work. This variant also takes away most, if not all social time in the evening; social time will have to be traded with the long wake gap between cores depending on personal preference.[[File:Siesta-hybrid.png|center|thumb|Segmented-Siesta hybrid]]Alternatively, Segmented can be scheduled with one core at night and one core in the day. Only a success or two have been reported thus far. This variant looks like Siesta with a long daytime core, and both core sleeps miss out on the peaks. The dark period should be 2-3h before the night core, and continue for ~2h after this core to stabilize the circadian rhythm. Adaptations are rare and a lot more difficult than a regular Segmented schedule, because '''skipping both sleep peaks can greatly hinder quality sleep'''. Over the course of adaptation, staying awake during the graveyard and morning hours will be tough, and having a long sleep in the day immediately can shake up the current sleep habits, if they are very different from this scheduling (e.g, regular 7-8h monophasic exclusively at night, non-nappers). The personal sleep peaks may change with artificial melatonin onset as a result of this new Segmented habits, however this entrainment will likely require an extended period of time for the circadian rhythm to be completely rotated.

===Third shift===

===Third shift===

[[File:Shift Work.png|center|thumb|A Variant for Third Shift]]Very little is known about this scheduling method, and adaptations have been overall not rewarding. The nature of third shift often brings about changes in many health aspects, including higher risks for cardiovascular diseases, increased stress, lowered immune system and hypertension in the long run, including a monophasic pattern. Adapting to a Segmented pattern without the natural habit will result in a very risky adaptation. There have been at least a couple failures while deploying Segmented sleep for shift work, however, '''success is very rare, only a case or two'''. The idea is to have a core sleep right after the work period, and a core sleep before work. The plan on paper sounds compelling, but the adaptation process is far from easy.

[[File:Shift Work.png|center|thumb|A Variant for Third Shift]]Very little is known about this scheduling method, and adaptations have been overall not rewarding. The nature of third shift often brings about changes in many health aspects, including higher risks for cardiovascular diseases, increased stress, lowered immune system and hypertension in the long run, including a monophasic pattern. Adapting to a Segmented pattern without the natural habit will result in a very risky adaptation. There have been at least a couple failures while deploying Segmented sleep for shift work, however, '''success is very rare, only a case or two'''. The idea is to have a core sleep right after the work period, and a core sleep before work. The plan on paper sounds compelling, but the adaptation process is far from easy.

==Lifestyle Considerations==

==Lifestyle Considerations==

Given the '''extremely versatile ways''' of scheduling Segmented, there is a reason that Segmented sleep remains popular nowadays and has been succeeded by many polyphasic sleepers, from the most basic beginners to the most experienced veterans. A lot of brand new polyphasic sleepers often reflect on their inability to sleep in one chunk on monophasic sleep, and perpetually wake up in the middle of the night. The perfect solution would then be to start a Segmented adaptation as a result of the abrupt awakening. Thus, Segmented sleep would greatly benefit these groups of population.

Given the '''extremely versatile ways''' of scheduling Segmented, there is a reason that Segmented sleep remains popular nowadays and has been succeeded by many polyphasic sleepers, from the most basic beginners to the most experienced veterans. A lot of brand new polyphasic sleepers often reflect on their inability to sleep in one chunk on monophasic sleep, and perpetually wake up in the middle of the night. The perfect solution would then be to start a Segmented adaptation as a result of the abrupt awakening. Thus, Segmented sleep would greatly benefit these groups of population.

{{TNT|Polyphasic Sleep Schedules}}

{{TNT|Polyphasic Sleep Schedules}}

[[Category:Schedules]]

[[Category:Schedules]]