[Ref HK CAD 372]

What’s “Window of circadian low (WOCL)”?

The WOCL occurs around the time of the daily low point in core body temperature ‐ usually around 03:00‐05:00 when a person is fully adapted to the local time zone. In CAD 371(2nd edition), WOCL is defined as the period 0200-0559 individual body clock time.

Time in the WOCL when subjective fatigue and sleepiness are greatest and people are least able to do mental or physical work.

However, there is individual variability in the exact timing of the WOCL, which is earlier in morning‐types (larks) and later in evening‐types (owls), and may move a few hours later after consecutive night shifts.