BiphasicX

A flexible biphasic schedule, which does not reduce total sleep time compared to a personal monophasic baseline and heavily depends on natural individual sleep tendencies and a stable circadian rhythm.

BiphasicX

Biphasic-X
chart link Legend   Sleep   Dark period   Flexible sleep window
Total sleep	~7-9 hours (non-reducing, so depends on individual monophasic sleep need)
Proposed by	GeneralNguyen
Difficulty	Easy
Specification	Mainly 1 core and 1 nap. Sometimes more cores/naps can be used to reduce total sleep. Both cores and naps are flexible.
Former names	Prototype X, Experimental X

Mechanism

This schedule is named to differentiate itself from other established biphasic patterns (Siesta, Segmented and E1). The suffix "-X" denotes variability in the daytime nap duration, which does not have to be a fixed duration everyday.

This flexible Biphasic schedule contains 2 sleeps per day (for the vast majority of days) without reducing the total time spent in bed. For example, a person who needs 8 hours of sleep each day can have a 6 hour core sleep at night and 2 hour siesta during the day. It has a lot of variations and flexibility in scheduling and has actually been done in the past in a way or another. For example, the experimenters reported certain positive results – sleeping 4 hours at night and 2 hours during the day (resembling Siesta), or 2 4-hour blocks (resembling Segmented sleep) was tested and results were shown to be positive short-term. Regarding daily lifestyle, many may find themselves naturally biphasic sleepers with a main core sleep at night that covers most or all of their SWS and REM need, complemented with a nap of varying lengths during the day depending on how sleepy they are.

One reason why people come to polyphasic sleeping and attempt other sleep-reducing schedules is to gain more wake time each day, not knowing that non-reducing polyphasic schedules are also viable alternatives. Thus, there have been few official attempts for this schedule that have been fully logged and reported up to date (all of which are at least somewhat positive experiences), due to the unappealing aspect of not being able to reduce a lot of hours spent sleeping. However, it has the potential to naturally reduce a tiny amount of total sleep each day with entrained biphasic sleeping and dark period; this theory still requires a big enough sample size to confirm if some sleep reduction is possible.

Scheduling principles

This schedule applies most of the fundamental concepts of polyphasic sleeping while having flexibility of its own:

• Most days contain 2 sleep blocks, with the main core sleep at night sustaining wakefulness for a long period of time while having added benefits of a nap during the day for a quick refresh.
• Short nap lengths (> 10 minutes and < ~25-30 minutes) contain only light sleep to sustain wakefulness into later times of the day. Longer sleep blocks (> 60 minutes) do contain both SWS and REM. Although there is no REM sleep in short naps, being able to fall asleep and getting some NREM2 is still beneficial for some recovery effect and aid in memory and learning with alertness boost. On days when there is a natural wake from the core earlier than usual (~1h) and the sleeper cannot go back to sleep, it is then wiser to get up and start the day. When nap time arrives, the nap duration can then increase, up to 2h (resembling Siesta daytime core) to compensate for the earlier wake than usual in the morning. If core duration is already close to personal monophasic baseline, then the nap will automatically shorten (resembling E1 naps). On this schedule there is no requirement to stick to any nap durations as they can last anywhere from 10m to 2h depending on day and the current level of homeostatic pressure before the daytime sleep, which factors in exercising, stress levels, etc. to dictate nap duration.
• Busier days allow for some sleep reduction in the main core sleep and more than one nap can be added to the schedule to maintain alertness level (detaching from Biphasic form and becoming different polyphasic forms such as E2, E3, etc but only on very few occasions). As a result of this, some following days are spent in recovery mode for extra sleep, done by either lengthening the nap or the core sleep (maintaining Biphasic form).
• The schedule fits most normal lifestyles that welcome taking a nap during daytime and learning to nap to later transition into other sleep-reducing polyphasic schedules with familiarized napping habits. Night sleep is the primary focus for health benefits and a daytime nap that fits into the circadian rhythm of natural energy dip in the afternoon or around noon. It also favors people who cannot nap at the same time everyday with the exception of incapability to reduce total sleep time each day.
• The ideal setup would be having a fixed core length at night and a fixed time of when to nap and keeping consistent sleep times as often as possible. However, sleep times can be different on a daily basis with small variation if necessary (from day 1) as well.
• A consistent daily dark period is used to stabilize the circadian rhythm, starting at the same time everyday. Currently there are a couple polyphasic sleepers in the community who stay on this schedule for extra flexibility while getting a chance to learn to nap and recharge from a nap during the daytime; they also reported to have very few issues with the schedule. The main structure sets this schedule up with extra protection for night sleep by avoiding any sleep past ~6 PM to facilitate falling asleep at night.
• During recovery days to recover from lost sleep or sickness, it is also necessary to have night sleep placed after dark period has started some time like normal days to not mess up dark period and night sleep timing. If dark period for example is set at 10 PM, place the night sleep at no earlier than 11 PM for all days regardless of sickness.

With enough time and certain consistency in sleeping twice per day, ideally the sleeper will become accustomed to biphasic sleeping, being able to wake up from both the core sleep and daytime nap without using any alarms even with different sleep times each day, without messing up night sleep or affecting quality of the daytime nap. Total sleep time will also become consistent with only small variations from day to day. NOTE: Biphasic-X is not to be confused with Random Biphasic where a sleeper would sleep twice everyday whenever they want, without any regards for circadian rhythm. This is ill-advised and should not be attempted.

Despite its seemingly natural tendency of sleep behavior in humans (non-reducing biphasic, with a daytime siesta), it did not officially record any forms adaptation or any adaptation success until early 2020, when there were a lot of successful attempts. These adaptations were confirmed with the currently used system of adaptation success criteria, like any other polyphasic schedules. The first detailed report as proof that this schedule works in the long term can be found here (45 days). A follow-up (~20 days after the first report) can be found here.

Polyphasic Sleep Schedules Scheduling overview Biphasic E1 Extended Siesta Segmented BiphasicX Everyman E2 Extended E3 Extended E4 Extended E5 Sevamayl Trimaxion Dual core DC1 Extended DC2 Extended DC3 DC4 Bimaxion Tri core Triphasic TC1 TC2 Nap only Uberman Dymaxion Tesla Spamayl Experimental QC0 Ducamayl Camayl Hypothetical Non-polyphasic Monophasic Random