Nap only

A nap-only schedule is simply a sleep schedule without cores.

Mechanism

Since REM and SWS cannot realistically be cut, all (or at least as much as possible) of them must be accounted for by naps. The extremely low total sleep time means it requires intense sleep compression, possibly reducing the cycle lengths to under 60 minutes. After adapting, falling asleep becomes very quick and the transition to REM or SWS would also be almost immediate, giving nearly negligible amounts of light sleep. This would allow up to about 1h50m of REM and SWS combined. Even so, this is still far below the combined requirements for most people, which means REM and/or SWS have to be cut in order to maintain this schedule, which is considered unhealthy.

Living on this schedule requires constant maintainence of a delicate balance between REM and SWS pressures. Throughout each waking block, REM and SWS pressures build up gradually to very high levels and drops to more withstandable levels during the course of a nap, which would primarily contain the sleep type with higher pressure. Then, this reverses the ratio between REM and SWS pressures, so that the other sleep type dominates the following nap. It is also likely to experience mixed-stage naps that resemble mini-cycles, with both REM and SWS in the body’s effort to mitigate high sleep pressure.

Since maintaining the schedule involves such high levels of sleep pressure, circadian rhythm is much less important than on other schedules with peak-aligned sleeps, making it possible to have SWS-filled naps in REM peak hours and vice versa.