The Biology of Sleep Cycles

Sleep is not a uniform state of rest; rather, it is a complex biological process consisting of several distinct stages that repeat in cycles throughout the night. A typical sleep cycle lasts approximately 90 minutes and moves through various phases, including light sleep, deep sleep, and REM (Rapid Eye Movement) sleep.

Why 90-Minute Intervals Matter

The goal of a healthy sleep routine is to complete five or six full sleep cycles. By timing your wake-up call to coincide with the end of a 90-minute cycle, you are waking up during a lighter stage of sleep, avoiding the grogginess of sleep inertia.