The 90-Minute Rule
Human sleep isn't just a single block of hours; it consists of 90-minute cycles transitioning through light sleep, deep sleep, and REM (Rapid Eye Movement). Waking up in the middle of a deep sleep cycle leaves you feeling groggy, regardless of how many hours you actually slept.
Why Calculate Cycles?
- Wake Up Refreshed: Timing your alarm for the end of a 90-minute cycle helps you wake up naturally.
- Optimize Rest: Aim for 5 to 6 full cycles (7.5 to 9 hours) for optimal cognitive performance and memory.