Flexible Sleep Timing

This page is an expansion from the Advanced Scheduling Section on the concept of flexing sleep. The strategies of flexing sleep documented in this page are based on past experiences of successfully adapted polyphasic sleepers and as such, are mostly experimental ideas with the hope of making polyphasic schedules flexible and adaptive to daily lifestyle. Being able to move polyphasic sleep blocks around is very appealing, and if pulled off successfully it will help polyphasic sleepers maintain their sleep schedules. This is especially beneficial if these sleepers have successfully adapted to their respective schedules and want to pursue the napping lifestyle in the long term.


Flexible sleep timing (often shortened to just “flexing”) is defined as moving sleep times from day to day, without changing sleep lengths of the sleep blocks. This definition mostly applies to reducing polyphasic schedules (schedules that reduce total sleep time compared to personal monophasic baseline) rather than non-reducing polyphasic schedules (which are inherently more flexible with more varying sleep lengths and random characteristics). The reason is that non-reducing schedules have a high amount of light sleep and total sleep as a whole, so it is easier to move sleep blocks around, shortening or extending a sleep duration without heavily affecting the inherent sleep architecture thanks to the light sleep buffer. This is especially true in the case of monophasic sleep (also non-reducing) because humans can sleep at different hours of the day in one go until they wake up. This allows the body to rake in an ideally sufficient amount of vital sleep stages, at the expense of a much longer sleep duration.

Therefore, the concept of flexing in polyphasic sleep only demonstrates its use in reducing sleep schedules, where vital sleep stages are preserved (after the adaptation phase) but a certain amount of light sleep (mostly NREM2) is reduced. Because of this, flexing a reduced schedule requires proper timing, skills, sense of time and maintenance of all sleep blocks. Additionally, flexing sleep is a powerful tool that can help sleepers maintain polyphasic schedules in the face of changing daily timetables that collide with the usual sleep times. This article will hopefully help polyphasic sleepers maintain their adapted polyphasic schedules. Approached properly, they will not have to revert to monophasic sleep if their daily timetable sometimes clashes with their usual sleep times. Currently, flexing mechanics are not fully understood especially when different sleep patterns are taken into account, and for beginners, flexing can be a rather challenging topic to understand.

Mechanics of Flexing Sleep

  1. Adaptation Mechanics:

One would wonder whether it is possible to adapt to a flexible polyphasic pattern, just as with rigid schedules. And if it is possible, would the adapted state on a flexible schedule be the same as that on a strict schedule? The general rule of thumb is that a full adaptation to a strict schedule is required, ideally staying adapted for several weeks (4-6 weeks), before one attempts to flex any sleep blocks. After this is done, it is possible to attempt to gradually move sleeping times of one or more sleeps, from day to day. After being comfortable with a small flex range, sleepers can then increase the flex range gradually to adapt to the new flex range. This information is also indicated in the book Ubersleep by Puredoxyk regarding the adaptation process to Everyman schedules as an example. Thus, adapting to flexible, reducing schedules for the most part requires two separate adaptation steps:

  1. Strict base of a schedule
  2. Flexing sleep blocks

This second step – a flexing adaptation – is usually tamer than the first step, and usually feels comparable to Stage 4 of a general adaptation. Personal well-being and productivity are slightly hindered and uncomfortable as a result of some manageable amount of sleep deprivation/mild tiredness as the body gets used to new sleeping hours. Successfully adapted flexing sleepers so far don’t report the full-blown sleep deprivation in Stage 3 that is almost always a part of adapting to a strict schedule. Through this incremental flexing method, sleepers have been able to become fully accustomed to flexible sleep times from day to day as repartitioning becomes stabilized. However, the full adaptation to flexing varies, and may take longer to complete than the first adaptation step, depending on the flex range, difficulty of base schedule, number of sleep blocks being flexed and the possibility/range of a flexed core. When flexing first begins, polyphasic sleepers can experience certain tiredness dips around the originally scheduled sleep time as sleep time is changed. Bigger flex ranges will take longer to fully adapt to than smaller flex ranges. A full adaptation to flexing can take 4-8 weeks like a regular adaptation, with few oversleeps.

NOTE: It is important to keep flexed sleep blocks at least 90 minutes apart from each other to avoid forming interrupted sleep, whether the gap is between the nap and the core or between naps. However, during emergency situations where sleep has to be obtained, this rule might be compromised.

Cold turkey adaptations to flexible schedules as documented in the community over the years largely lead to failures. Theoretically, this is because the body fails to recognize sleep times and the repartitioning of vital sleep stages cannot be completed, leading to an incomplete adaptation state, hovering between Stage 3 and 4. However, it is worth noting that very experienced polyphasic sleepers who have already adapted to a polyphasic schedule and then flexed the sleep times successfully in the past may be able to flex times slightly during new adaptations. If they are unable to do so, they will likely be able to start flexing nearly immediately after the new adaptation is complete, as opposed to beginners who often require more time to adapt. Thus, beginners are highly discouraged from attempting to flex sleep during adaptations to strict schedules.

  1. Total Sleep Time:

Depending on the total amount of sleep scheduled, flexing may require permanently adding 30 or 90 minutes to a core, to buffer the reduced sleep efficiency of flexed sleep. This is particularly a problem for schedules with very low total sleep times (e.g, Everyman 3, Dual Core 3, Uberman). Currently, it is recommended that a base schedule can become flexible with a minimum of 5.5 hours of total sleep, assuming that personal monophasic baseline is around 8 hours. People with a higher monophasic baseline (at least ~9 hours) may have a more difficult time flexing a regular 5.5-6 hour polyphasic schedule. This is because of a greater reduction in light sleep amount; thus, flexing a sleep block should be done either sparingly or with a cautiously narrow flex range. As a known exception, several adapted Everyman 3 sleepers (4.5 or 5 hours total sleep) have been able to flex their 2nd and/or 3rd naps with a stable core sleep and fixed first nap.

Below are some tricks that facilitate flexing sleep in regards to total sleep time:

  • Increase core length by 30 minutes: This can typically be seen in Everyman 2 core (5 hours) or Everyman 3 core (3.5 hours). The sleep cycle length varies for everyone, and a 3.5 hour core has been proven to work, so it is a viable option. The 5 hour core is theoretically in line with the statistically-likely REM period: with proper sleep hygiene and normal sleep requirements, SWS usually occupies the first 3 cycles of a core in the night, and REM sleep usually takes over the first part of remaining cycles. This small addition of sleep duration to a core length may make room for more REM sleep and protect REM requirements on the whole schedule more easily, despite flexing.
  • Permanently increase core length by 90 minutes (a full cycle): This gives more light sleep buffer and alleviates homeostatic pressure on the other sleep blocks, and facilitates flexing sleep.
  • If there is more than one nap on the schedule, avoid flexing the first nap: This rule applies to Everyman schedules or schedules with a nap between 6-9 AM. This nap is primarily filled with REM sleep and usually contains little light sleep thanks to the circadian timing of REM sleep, so it is necessary to preserve its quality by avoiding flexing it as much as possible. However, experienced polyphasic sleepers can flex this nap to some degree.
  • Avoid flexing the core, or only to a small degree depending on the schedule. A core sleep is a “core” for a reason – it contains a lot more vital sleep stages than a power nap along with some amount of light sleep buffer. Drastically moving the core sleep around alters circadian influences on cycle architecture as well as affecting the homeostatic pressure for the following sleep blocks. Changes in the overall sleep architecture can lead to destabilization. For example, an Everyman 2 core from 23:00 to 03:30 should not start at 01:00 (flex range of 2 hours) or later. However, if a big flex range has to occur (on very rare occasions) and the sleeper has been solidly adapted to the schedule for a long time, then it is possible to overcome this large flex range and gradually recover the following days. Currently, it is theorized that schedules with more than one core sleep and a total sleep of at least 5.5-6 hours tolerate core flexes better than Everyman schedules where there is only one core sleep. For instance, a second core can be useful in compensating for inconsistencies in the first one. Schedules with a core sleep of ~6h or longer may also make flexing easier at least to a small degree. Similar to nap flex, core flex should begin with small flex ranges (~15-30m in either direction) and then increase the flex range incrementally to gradually adjust to the new sleep times.
  • Avoid placing naps close to the core sleep during flexing. Short naps evoke more grogginess if placed around SWS peak, graveyard hours or evening hours. They may contain SWS and result in heavy sleep inertia upon awakening. As a result, placing flexed naps from 19:00 to 03:00 is not recommended for schedules with a core sleep at night. Having late naps may also increase sleep onset latency for the core sleep at night, resulting in difficulty falling asleep and potentially ruining the core.

Conclusively, it is important to consider the total amount of sleep on the base schedule before devising a plan to flex sleep blocks. Attempting to flex schedules with a low amount of sleep (e.g, difficult adaptation to base schedule or maintenance of well-being on base schedules) can destabilize the whole schedule and lead to oversleeps, pushing the sleeper back to the previous sleep deprivation stages.

  1. Differences between “-flex” and “-amayl” schedules:

Polyphasic schedules tend to become more flexible after the first strict adaptation step is completed, although to varying degrees. Currently, there are 2 different systems of flexible schedules. This section will differentiate between them.

  1. Flexible Schedules:
    Flexible Everyman 2 Extended (E2-Extended)

Figure 1. Flexing Everyman 2 Extended (E2-Extended)

The above napchart shows an E2 variant with a flexible second nap. This nap has a flex range of 90 minutes in either direction, suggesting that the sleeper can take the nap 90 minutes sooner or later than the regularly scheduled strict time from the first adaptation to the E2-extended base, depending on day. The flex range also indicates that the sleeper has been able to flex the second nap with any range smaller than +/-90 minutes (e.g, 40m sooner or 60m later than the original time) if desired. However, in this case the core sleep and the first nap are kept at the same hours as the original sleep times. The remaining waking hours are untouched. Similarly, other regular, slightly flexible schedules will have at least one flexible sleep block while the remaining waking hours resemble those on the first strict adaptation.

  1. -amayl” (“as much as you like”) schedules:

These schedules (e.g, SEVAMAYL) require that sleepers have highly enhanced flexing skills to the point that they are comfortable with sleeping around the clock while maintaining productivity, well-being and other successful adaptation criteria. The defining distinction is that “-amayl” schedules have somewhat variable numbers of sleep blocks from day to day, within a certain general structure. For example, SEVAMAYL will have 1 core but a variable number of naps, similar to a general Everyman schedule’s structure. “-Amayl” sleepers have become capable of sleeping whenever they’re tired enough, because their sleep remains efficient enough to provide the necessary vital sleep stages. “-Amayl” schedules, despite their versatility, require paying some attention to wakefulness and alertness dips; sleepers should rest after getting somewhat tired, but before getting too tired and risking an oversleep. The close monitoring of homeostatic pressure to achieve efficient sleep can make “-amayl” schedules difficult to manage across a wide range of possible sleep times. An example of a SEVAMAYL variant is shown below.

SEVAMAYL as an "-amayl" schedule and the flexible rangeFigure 2. SEVAMAYL as an “-amayl” schedule

The SEVAMAYL sleeper as illustrated in the above napchart is able to flex the core by 60 minutes in either direction, as well as flexing all the naps to various degrees, to the point that any naps placed between 05:15 and 19:00 are comfortably adjusted. Because of SEVAMAYL mechanics with a core sleep at night, evening hours are spared from napping while the freedom to nap whenever tired during the daytime hours is very satisfying. In order to adapt to SEVAMAYL, a strict adaptation to a base Everyman schedule (e.g, E3-extended) is required. After that, adapt to the flexible intermediate E3-extended with gradual increases in flex range of each sleep block, and finally SEVAMAYL.

Adaptation-wise, “-flex” schedules are good intermediate steps for adaptations to “-amayl” schedules to help ease polyphasic sleepers into flexing sleep. All successful adaptations to flexible schedules take place after a successful adaptation to the strict base (e.g, flexible nap from E1, DC1-ext nap or either of the 2 cores from DC1-ext). Rare exceptions exist, especially for those with genetically reduced monophasic sleep requirements. Because of the massive flex ranges of sleep blocks seen on “-amayl” schedules, adaptations to them are expected to be harder than to flexible schedules.

As an additional aspect of schedule malleability, adapted “-amayl” schedules may include somewhat variable sleep block lengths, which is facilitated by having fewer or more sleep blocks on any given day. Normal, reducing flexible schedules do not seem to support variable sleep block lengths, as this can affect repartitioning of vital sleep stages in each sleep block. It’s too difficult to retain well-being with a defined number of naps that should each last less than about 23 minutes (e.g, Everyman), while drastically altered architecture of the core sleep also makes reliable compensation difficult without variable numbers of sleeps. Likewise, not any schedules can take the “-amayl” form. Any schedules have to be able to show the ability to change the number of sleep blocks from day to day or at least done so comfortably occasionally and maintain polyphasic characteristics to be considered “-amayl”. For example, a Segmented pattern with 2 core sleeps of 3 hours each cannot become “Segmented-amayl” because if one of the 2 cores is skipped on some days, the whole schedule would become monophasic sleep. This concept is demonstrated in an example below.

CAMAYL with an average of 4 cores each day and the flexible rangeFigure 3. CAMAYL with an average of 4 cores each day

The above napchart represents a CAMAYL [link to CAMAYL page] version with usually 4 core sleeps each day and the sleeper has demonstrated the ability to sleep for 90 minutes whenever tired enough. However, on days where one of the core sleeps has to be skipped because of personal reasons, the schedule takes the following form below.

Triphasic base & an extra core the following day on ht flexible CAMAYLFigure 4. Triphasic base & an extra core the following day on CAMAYL

Once adapted, skipping one core for a day only raises homeostatic pressure to reasonable levels with the increased wake gap. It is then possible to make up for the lost core by adding a core the following day (taking 5 cores instead) to recover from the lost sleep the previous day. This is equivalent to taking 4 cores on usual days. Alternatively, extending one of the cores to 3 hours can also do the job if scheduling 5 cores is too challenging. Similarly, the lowered number of naps on SEVAMAYL on some days enable the core to be extended by 90 minutes or extra naps to be added the following day as a way to rebalance homeostatic pressure.

Lifestyle Consideration

Despite the inherent advantages posed by flexible schedules after the first adaptation step, it is necessary to consider appropriate lifestyles to afford either flexible or “-amayl” schedules. There are two scenarios that flexible sleepers will have to face in their lifestyle: Sleep when tired enough, and sleep when required to. This section will detail different strategies to make use of sleep hours in various settings in hope of maintaining flexible polyphasic schedules.

  • Appetitive napping: This napping method is common in “-amayl” schedules, or it can work occasionally in flexible schedules when flex range has become wide enough. In anticipation of events that are unpredictable on certain days, sleepers can lie down for a short nap (including naps less than 20 minutes) even when not tired enough for a usual nap/core. This situation works for experienced and long-term adapted polyphasic sleepers who can turn a shuteye into actual naps even without feeling very tired. Having small power naps allocated at specific hours where a small break gap is allowed makes a good environment for appetitive naps. Even if only NREM1 is obtained from the nap, it can subjectively sustain wakefulness and performance to the next sleep block should the current timetable allow it.

Appetitive nap on flexible DC1-ExtendedFigure 5. Appetitive nap on flexible DC1-Extended

The above scenario indicates the possibility of napping outside the adapted flex range once in a while if there are certain interruptions that prevent any sleep in the flex range. For example, it’s useful when there is only one small work break for a nap. The adapted DC1 sleeper may not sleep as well as they would in the flex range, but getting some sleep when they can is necessary to sustain wakefulness for busy hours that require concentration and performance. There is no time for a nap after the busy block; a nap then would interfere with the core sleep at night. If there is some time to cool down before the nap, regular tips on how to fall asleep during naps still apply (e.g, wearing eye masks, finding a less noisy nap spot, focusing on breathing).

  • Prophylactic Napping: This is a term for how to effectively have a nap early, with minimal problems during a long waking gap. Instead of skipping the nap, adapted sleepers can arrange a nap earlier than usual to help stay awake. However, in order to make a prophylactic nap effective, sleepers are required to actually fall asleep in the nap. This may require prior sleep blocks be taken slightly earlier before the prophylactic nap and long waking gap. An example is demonstrated below.

Prophylactic nap on flexible E3Figure 6. Prophylactic nap on flexible E3

In this example, the second nap is moved out of the regular flex range to right before the Busy period. As shown in the napchart above, the adapted E3 sleeper can flex the first nap 45 minutes earlier than usual (Adjusted 1st nap) to make use of the second nap. Skipping the second nap entirely may be devastating to the schedule and is not the only option if there is room to make use of flexing. However, even if the flexed nap is done successfully, there is still a chance that the nap quality will be lowered and lighter. This can increase the sleep inertia after the last nap of the day, or increase the amount of REM in the core. As a result, it may take some days of consistency to recover from the lost amount of vital sleep stage if sleep deprivation signs occur.

  • Consistent food intake and exercise window: Despite the flexibility of sleep timing, it is still possible to schedule meals and exercise times rather consistently. If a nap is to be scheduled slightly later than usual, it is a good move to eat right after waking up (e.g, lunch). This avoids conflict with the next sleep block in case it’s too soon afterward. Eating too close to sleep time has been observed to decrease sleep quality, so it is best to avoid this scenario and spare 2-3 hours from eating before each sleep, especially the core. Similarly, exercises can be done after waking up from a flexed nap/core to prevent it from increasing sleep onset of the next sleep blocks (e.g, the core at night). Exercise before sleep keeps many people awake. However, exceptions can be made on certain schedules where adapted sleepers are aware that a certain nap on their schedule contains only NREM2 consistently (e.g, flexible E1 nap or the second nap of E2). When time is crunched, a meal can be scheduled ~1 hour before nap time; as long as the sleepers can fall asleep in their naps, they will get NREM2 regardless. However, if the nap is found out to contain some vital sleep stages (e.g, REM sleep), it is necessary to plan meals at least ~2-3 hours ahead of each nap to protect its quality.
  • Reduce the flex range for work days: This applies to sleepers who have a fairly consistent schedule on work days throughout the week. The timing of each sleep block only varies within a small flex range during these days, and can be flexed in bigger ranges during weekends or holidays. For example, a daytime nap may only be flexed 15-30m back and forth, around the original nap time in the strict base schedule. This eases prediction to schedule sleep times around certain hours with a familiar pattern of energy dips. For those with a consistent daily lifestyle, being adapted to, or aiming to adapt to a flexible schedule seems more appropriate than to an “-amayl” schedule if the flex range is usually only small. This also goes with an easier flexing adaptation if a slightly flexible schedule is chosen. The purpose of “-amayl” schedules is usually lost with a consistent timetable from day to day, which automatically limits the flex range of each sleep block and eliminates the freedom to sleep whenever tired enough. Thus, it is necessary to look over individual lifestyles carefully before planning to adapt to either flexible or “-amayl” schedules.

Flexible E2 & work daysFigure 7. Flexible E2 & work days

This is an example about an adapted E2 sleeper who manages to have a flex range of 70 minutes in either direction for the second nap and 30 minutes in either direction for the first nap. Upon sketching his new daily work schedule after the flexing adaptation, he decides to reduce the flex range during weekdays to comfortably predict the second nap to fall between 14:15 and 15:00 to not disrupt the consistent work schedule. During weekends, he can increase the flex range of both naps to the previously adapted wider flex range should new events arise.

In conclusion, flexing sleep can be a challenging yet necessary skill to acquire if one decides to maintain the polyphasic lifestyle long term. It takes efforts, vigilance, a clear sense of personal wakefulness, tiredness dips and solid adaptation skills to make flexing a truly viable lifestyle. Flexing sleep requires two separate adaptation processes, with the second step being potentially longer yet milder than the first. Sleepers are recommended to assess their daily timetables to determine whether a flexible or an “-amayl” schedule should be chosen. Currently, it is usually regarded that flexing the core sleeps is more difficult than flexing short naps, thus some flexing experience for beginners is required from flexing naps before they attempt to flex the core sleep. It is also important to consider total sleep time on the base schedules, duration of staying adapted on the base schedule, exercise, food intake and certain unpredictable events to schedule each sleep block properly.

Main author: GeneralNguyen

Page last updated: 23 July 2020