The Tri Core family of sleep schedules are relatively unusual and not very popular due to hard scheduling along with wake time activities. The schedules in this group have an SWS-focused core, a REM-focused core, and a mixed core, all of which are a single cycle in length. The number of naps is also very low compared to other schedules (between 0 and 2).
A perk of these schedules is that a good amount of multiple types of sleep are distributed across the day, which aids in sustaining wakefulness and minimizing homeostatic pressure. The short single-cycle sleep blocks can help promote greater levels of sleep compression, which may help with raising the sleep quality that would otherwise only be seen on schedules with much smaller sleep quantities like Everyman 4/5, Dual Core 3/4 or nap-only schedules.
- Adaptation difficulty: Somewhat hard
The original, traditional and most well known tri-core schedule, Triphasic, was proposed by Leif Weaver. It consists of 3 single-cycle sleep blocks which are spread equidistantly throughout the day – one sleep cycle every 8 hours. So in each 8 hour block, you get 6.5 hours awake and 1.5 hours asleep. One could view this schedule as combination of segmented sleep with late siesta core. The equidistant spacing is not compulsory and some people have been able to adapt to a spacing of 8-9 hours between some cores without significant issues. Non-equidistant scheduling is discouraged for people who lack polyphasic sleeping experience.
This schedule has no naps at all, and requires a sleep block to be placed in the middle of the afternoon. This, along with the socially intrusive evening core, makes the Triphasic Sleep Schedule unpopular. However, it is the only seriously viable sleep pattern with significant sleep reduction that will give high levels of sleep compression without having to take any naps. Sometimes the sleep blocks might see natural wakes after only ~1h or so, which is indicative of the level of compression that can be achieved on this schedule.
Some caution is advised when adapting to Triphasic, because only a single cycle is placed in an SWS-favourable time period. For this reason, people who try to adapt to Triphasic might experience SWS deprivation symptoms during adaptation. This, with addition of the shortened cycle length, can make waking from the night time core very difficult, since there is a very high chance of waking up from SWS. After adaptation, this should not cause problems anymore, but during the adaptation it will be more difficult to avoid oversleeping. It is worth noting that very few people have adapted to this standard version of Triphasic, as most people tend to get the SWS core naturally extended while the afternoon core shortens, resembling a modified Dual Core 1.
In the event of sickness or temporarily high SWS need, the night core can sometimes be extended by an extra cycle without completely breaking the schedule after adaptation, although some sleep compression will be lost from this and it may take some days to recover from the damage. An extended version of triphasic should add a cycle to the SWS evening/night core.
- Adaptation difficulty: Moderate
This variation of the Triphasic schedule was prototyped by the Polyphasic Discord community in 2017 and is one of the newest known viable schedules. The idea behind this schedule is that the cores are moved to typical night time sleeping hours only, which removes Triphasic’s inconvenient core sleep during the afternoon.
Because the 4.5 hours of core sleep does not allow for over 12 hours awake in a row, a nap must be added to compensate for the closer spacing of the cores. The added nap is usually placed right in the middle of the waking block, at the same time as the afternoon core of Triphasic would be.
SWS deprivation symptoms during adaptation are less likely to be present on this schedule than on Triphasic, because the mixed core in the night is likely to allow for higher amounts of SWS. For ideal scheduling the cores should have a gap of at least 2h, preferably 3h, as some people might not be able to adapt to a gap that is less than 2 cycle lengths long. Tricore 1 can also be used during gradual adaptation as a transitional schedule into Dual core 3 by reducing the third core into a nap and adding a nap in the middle of the day.
- Adaptation difficulty: Moderate
This tri-core variant (proposed by LichTerLoh via the Polyphasic Discord) places the mixed core in the very late afternoon, the SWS core just before midnight and the REM core at dawn. It is complimented by 2 naps, one placed in the morning and one in the early afternoon.
It can be used to adapt to Dual core 3 via rhythmic preservation by adding a nap and reducing the core which feels like the lightest/most unnecessary one into a nap after adaptation.