what qualifies as a core in polyphasic sleep
A core sleep of minimum duration

A core sleep typically contains a multiple of 90 minutes on a polyphasic schedule. After multiple weeks, many polysleepers find themselves waking up earlier than expected for 90-minute cycles. If this happens, they can safely reset their alarms to reflect shorter sleep cycles. Humans often have a sleep cycle of 80-120m. 

However, other schedules like Dual Core 1 can lengthen sleep cycles of cores instead.

Placement of Core Sleep

Core placement matters because most schedules rely on cores exclusively for SWS sleep.

  • Core length till alarm matters because you definitely want to wake in light sleep every time.
  • Waking in an SWS block strongly risks falling back asleep, or not waking at all.
  • Waking during REM is alright, or may be desirable for dream recall. However, it does carry more sleep inertia especially during Stage 3.
  • Waking comfortably during light sleep won’t happen consistently during the adaptation process; by definition it will after about 4-6 weeks if adaptation is successful.


  • The more separate cores you have, the more opportunities to place each core at an ideal point for circadian peaks and reset the homeostatic pressure
  • A core overlapping from 21:00 to midnight will likely maximize on SWS,
  • Likewise, a core between 06:00-9:00 will carry the most amount of REM sleep.

However, this alignment of sleep stages only exists if your light exposure and activity go along with sunlight. People often disturb or alter their circadian rhythm with artificial light or excessive adrenaline/stress. As a result, this can alter when these peaks occur. They can occur later than they otherwise would. 

Core Sleep Duration

Core cycle length matters as you progress in adaptation.

  • Start with 90m cycles by default.
  • After some weeks, if you consistently begin waking early, you can assume that your sleep cycles are naturally becoming shorter. Many polyphasic schedules have this effect. Coincidentally, this appears to increase with shorter sleep times. In addition, you can eventually set your alarms earlier to reflect the shortened sleep cycles.
  • One can also increase core lengths by 30 minutes after the 2nd or 3rd cycle of the night. This will smoothen the adaptation as well as allow for greater day-to-day flexibility of sleep times after adaptation. The downside is, apparently, a slightly higher total sleep.

Main authors: Crimson & Aethermind

Page last updated: 5 January 2021