时程编排概述
时程编排睡眠安排涉及许多方面，是一个复杂的话题，必须根据个人的需要进行调整。如果多相睡眠时程设计得不好，十之八九会导致严重的睡眠不足，而且很可能一直无法适应，浪费几周甚至几个月的时间。这页会详细介绍目前关于多相时程编排的共识。
睡眠阶段
睡眠是一种会为身体整体带来生理上的变化的复杂现象。然而，它主要影响的是大脑。根据大脑中的电活动，睡眠被分为快速动眼期（REM）和非快速动眼期（NREM）。 NREM睡眠根据脑电波的频率和振幅再被进一步分为三个阶段。
NREM第一阶段占单相成人总睡眠的5至10%，是所有NREM阶段中最浅的睡眠阶段。在这个阶段中，对外部环境和对自身的意识都会有所减弱。部分人在这个阶段会出现抽搐或临睡幻觉。 NREM1中Alpha波和Theta波会混合存在。
NREM第二阶段是比第一阶段更深的睡眠，占总睡眠的45至55%。与NREM1相比，在NREM2中更难被唤醒。这个阶段的特征是K-复合波和睡眠梭状波，即Alpha波活动的突然中断。这阶段的睡眠也负责维持长时间的清醒状态。
NREM第三阶段占总睡眠的15至25%，是所有睡眠阶段中最深的阶段。这个阶段主要包含高振幅和低频率的Delta波。因此，它也被称为慢波睡眠（SWS）。要从这个阶段中醒来是非常困难的。试图这样做往往会导致一段强烈的呆滞和认知功能受损的时期——睡眠惰性（sleep inertia）。 NREM3通过胶淋巴系统（glymphatic system）在维护大脑方面发挥着关键作用。这过程需要约30至60分钟的连续的NREM3才能完成，因此只包含短暂小睡的时程可能会阻碍到此功能。
REM占总睡眠的20至25%，其特点是类似于清醒时的高频率、低振幅的脑波活动以及快速的眼球活动。在这个阶段，肌肉会被麻痹，体温亦会变得不受调节。 REM睡眠中经常会出现生动的梦境，而肌肉麻痹会使睡眠者无法将其行动表现出来。
透过多相睡眠缩短睡眠
SWS和REM（统称为“必要睡眠阶段”）是身体最需要的睡眠阶段，一般来说不能被削减。当睡眠者没有得到足够的SWS或REM时，相应的压力就会开始积累。随着压力的增加，身体会开始偏好于所缺乏的睡眠阶段而不是其他。一段时间过后，这可以引起入睡出现之快速动眼期（SOREM）和入睡出现之慢波睡眠（SOSWS），让身体能够在更短的时间内获得所需的SWS和REM。此外，当睡眠受到限制时，必要睡眠阶段会取代浅层睡眠（NREM1和2），进一步减少了维持健康所需的总睡眠量。
然而，随着NREM2的减少，长时间保持清醒的能力也会减弱。因此，总睡眠时间（TST）较短的时程需要有更多睡眠段落分布在一天中。约20分钟的小睡或约90分钟的单周期主段有助于多相睡眠者维持清醒状态。最大的觉醒间隔取决于你所选的时程、日程安排以及睡眠者的个人需求。如果间隔太大，你在这期间将会总是感到阵阵疲惫，进而无法完全适应时程。
昼夜节律
昼夜节律（Circadian rhythm）是体内的生物时钟，主要通过曝光和食物摄入等因素与当地的太阳时保持一致。它在一天中持续带动荷尔蒙变化，对身体产生影响。昼夜节律其中一个主要影响是褪黑素（melatonin）的分泌。它的存在对进入SWS至关重要，同时对REM的出现时间也会产生影响。
日落之后，当光照水平降低时，身体会开始分泌褪黑激素以促进睡眠。入夜时褪黑激素水平的上升让身体能在最初几个睡眠周期中获得SWS。相反，随着褪黑激素水平在早晨下降，REM就会成为被优先的睡眠阶段。
在现代，随着人工照明的出现，许多人的昼夜节律被推前了（即更晚）。然而，这种对人工照明的暴露也损害了人们有效获得SWS的能力。光对昼夜节律的影响程度由黑视蛋白敏感度函数（melanopic light sensitivity function）断定，该函数在480nm前后（蓝色）达到峰值，并在两侧下降。为了减少这种影响，睡眠者有必须采用一个暗期，在此期间，蓝色和绿色的光不能进入眼睛。这可以通过使用红色护目镜或荧幕过滤器等多种方式实现。
为了保持昼夜节律的稳定性，所有多相睡眠时程的主段或暗期时间都不能有太大的变化，必须每天保持相对的一致性。因此，非24小时周期的时程是不可持续的，更是不健康的。这方面的例子包括周期超过24小时（不断推迟睡眠阶段），或是每天采用完全不同的睡眠时程。
Minimum sleep threshold
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.
| Age | Recommended minimum sleep |
|---|---|
| <16 | 7.5 hours |
| 16-18 | 6 hours |
| 18-21 | 5 hours |
| >21 | 4 hours |
It is recommended that one stay above these limits at all times to prevent adverse effects on health. The necessity of vital sleep stages also implies that certain schedules, such as Uberman or Dymaxion, will be unachieveable for most people as its total sleep is below the total vital sleep required for most people.
Here is a basic classifcation of schedules by their difficulty level, assuming a typical sleeper with 8h monophasic sleep and normal levels of SWS and REM:
| Difficulty | Example schedules | TST range | Sleep time cut | Note |
|---|---|---|---|---|
| Easy | BiphasicX, E1-ext,
Siesta-ext, Segmented-ext |
7-8 | <1 hour | Recommended for beginners or those needing significant flexibility. |
| Moderate | E1, E2, E3-ext, Siesta, DC1, Triphasic-ext,
Segmented, DC1-ext |
5-6 | 1-2 hours | Require a significant adaptation process, but can be quite flexible after adapting. |
| Hard | E3, DC2 | 4-5 | 2-3 hours | Require harsh adaptations and are not particularly flexible for most people. |
| Very hard | DC3, Bimaxion, Triphasic | 4-5 | 2-3 hours | Considered harder than the "Hard" ones because they do not contain a longer core during SWS peak hours. |
| Extremely hard | E4, E3-shortened, Uberman, Dymaxion | <4 | >4 hours | Not considered possible for most people. |
Sleep block lengths
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 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 naps (up to ~45 minutes, known as pronaps) 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.
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 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
Two main schedule types have been practiced by humans since time immemorial: Segmented -- with two long sleep in the night separated by a wake gap, and Siesta -- one long sleep in the night and a shorter sleep in the afternoon. Of course, the schedule timings of the ancient people are more flexible and thus likely contains more total sleep than the current standard ones. Most current polyphasic sleep schedules evolve from monophasic sleep as well as the above two historically common schedules.
The Biphasic line of schedules consists of the two historical polyphasic schedules, as well as E1, which is also considered a variant of siesta in an Everyman style.
The Everyman line of schedules are formed by removing sleep cycles in the end of monophasic sleep, and adding naps to compensate for the lost time in REM and sustain wakefulness.
The Dual core line of schedules does the same thing, except to Segmented instead of monophasic sleep.
Over the decades, the polyphasic sleep community has developed several lines of schedules that have been known to work.
| Schedule line | Description | Notes |
|---|---|---|
| Biphasic | Two sleeps | Usually deemed the easiest and recommended to beginners. |
| Everyman | One core sleep and two or more naps | |
| Dual core | Two core sleeps and one or more naps | |
| Tri core | Three core sleeps | |
| Nap only | No cores and any number of naps | Not deemed to be achievable for most people. |
| Experimental | Those that do not fit into the above categories | Not usually recommended for beginners due to insufficient evidence of them working |
