Second wind (sleep)

Second wind (or third wind, fourth wind, etc.), a colloquial name for the scientific term wake maintenance zone, is a sleep phenomenon in which a person, after a prolonged period of staying awake, temporarily ceases to feel drowsy, often making it difficult to fall asleep when exhausted.^[1][2] They are the result of circadian rhythms cycling into a phase of wakefulness.^[3] For example, many people experience the effects of a second wind in the early morning even after an entire night without sleep because it is the time when they would normally wake up.

While most "winds" coincide with the 24-hour cycle, those experiencing extended sleep deprivation over multiple days have been known to experience a "fifth day turning point".