We are told life is a cycle. These words could not be truer than when they are applied to the biological processes that support and help life survive on the earth. One such cyclical process is the ultradian rhythm. We can observe these rhythms as physiological patterns that all living things — from single-celled creatures to humans — adopt to function properly.
While circadian rhythms such as the sleep-wake cycle follow a 24-hour cycle, ultradian rhythms are biological rhythms that recur more frequently than once every 24 hours. They govern various physiological processes, including heartbeat, breathing, hormonal release, and brain-wave activity. As such, ultradian rhythms play a vital role in orchestrating essential bodily functions.
One of the more better-known among them is the sleep cycle, characterised by alternating periods of rapid eye movement (REM) and non-REM sleep. Through the night, individuals cycle through these stages multiple times, with each cycle typically lasting around 90 minutes. During REM sleep, the individual dreams, while non-REM sleep is crucial for the individual to restore themselves physically and consolidate their memories.
Ultradian rhythms also influence patterns of hormone release, such as the pulsatile secretion of growth hormone, cortisol, and insulin. These hormonal fluctuations are essential for individuals to regulate metabolism, energy levels, and stress responses through the day.
