The content on this page was last updated and reviewed on Saturday 03 March 2018.
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The tri core family of sleep schedules is often seen as a weird outlier. The schedules in this group consist of 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 contrastingly very low (between 0 and 2).
The advantage of these schedules is that a fair amount of light sleep is distributed across the day, which helps to sustain wakefulness. The short single-cycle sleep blocks also help to promote higher levels of sleep compression, which help to raise sleep quality, and which would otherwise only start to be seen on schedules with much smaller sleep quantities like Everyman 4/5, Dual Core 3/4 or nap-only.
Adaptation difficulty: SOMEWHAT HARD
The most traditional and well known tri-core schedule, Triphasic, was invented by Leif Weaver. It consists of 3 single-cycle sleep blocks which are equidistantly separated throughout the day - one sleep cycle every 8 hours. So in each 8 hour period, you get 6.5 hours awake and 1.5 hours asleep. The equidistant spacing is not compulsory - some people have been able to have spacing of 8-9 hours between cores without significant issues (although this sort of scheduling is not advised for people who lack polyphasic sleeping experience).
This schedule does not have any naps whatsoever, and requires a sleep block to be placed in the middle of what is traditionally the afternoon. As a result, it does not tend to be all that popular. However, it is the only seriously viable sleep pattern with significant sleep reduction that will gives high levels of sleep compression without having to take any short naps. Sometimes sleep blocks might see natural wakes after only ~1h or so, which is indicative of the compression level that can be achieved on this schedule.
Some caution should be taken when adapting to Triphasic, because only 1 cycle is placed in an SWS-favourable time period. For this reason, people who try to adapt to the Triphasic schedule might experience SWS deprivation symptoms during adaptation. This, added to the reduced cycle length, can make waking from the night time core very painful, because there is a high chance of SWS wake. After adaptation is complete this should no longer cause problems, but during the adaptation it can make the schedule very hard to adhere to, as it will be more difficult than normal to avoid oversleeping.
In the event of sickness or high SWS need, the night core can sometimes be extended by an extra cycle without completely wrecking the schedule, although some sleep compression will be lost from this and it may take some days to recover from the damage.
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 concept behind this schedule is that the cores are moved to typical night time sleeping hours only, which avoids having to take a long core during the afternoon, one of the main reasons people are put off from trying Triphasic.
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 typically placed right in the middle of the waking block at the same time as the afternoon core of Triphasic.
SWS deprivation symptoms during adaptation are less likely on this schedule than on Triphasic, because the mixed core in the night is likely to allow for decent amounts of SWS.
Adaptation difficulty: MODERATE
This tri-core variant proposed by LichTerLoh 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 placed in the morning and early afternoon.
While technically a viable schedule, it doesn't really have much going for it at all and is probably best to be completely avoided.