Free-running sleep means:
- Go to sleep when tired.
- Wake up without an alarm.
Early studies on circadian rhythm showed that our internal clocks run on a 25-hour period when isloated from external stimuli like daylight and timekeeping. External cues like sunlight reset our circadian rhythm and math it with the 24 hour day. These cues are called zeitgebers. (Other zeitgebers are food,exercise, and social interaction).
Even with a 25h internal clock, humans have slept with the 24h day before alarm clocks were invented. Artificial light prolongs the internal clock. To wake up without an alarm clock, don't expose yourself to too much artificial light at night. That will shift your internal clock forward.
Many insomniacs have circadian rhythms that run on 26 or 27 hour periods. It is difficult to entrain a 27-hour internal clock with a 24-hour external clock. Solution: free-running sleep with 27-hour days. Go to bed when you're tired, wake up naturally. Obviously hard to manage if you're not self-employed or on vacation.
Studies show that free-running sleepers experience a 10-15% boost in creativity compared to those who use an alarm clock.
Health-wise, free-running sleep is the optimal sleep schedule. It can be synced with the 24h day, but with artificial lights(like computer monitors) it might run out of sync,which is OK too.
