Since [[wikipedia:Rapid_eye_movement_sleep|REM]] and [[wikipedia:Slow-wave_sleep|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.
+
{{TNT|Further|Nap only#Mechanism}}
+
Like other nap only schedules, Uberman requires extreme rigidity and sleep compression, which makes it one of the toughest sleep schedules.
