Ultradian Rhythms

Ultradian rhythms are repeated biological patterns that have a cycle of less than 24 hours. They are body rhythms that last less than one day.

Examples of ultradian rhythms include eye blinking, heartbeats, sleep patterns, breathing, pulse, appetite, digestion, temperature regulation, and some hormonal cycles. Ultradian rhythms are contrasted with infradian rhythms which are longer than 24 hours and include the menstrual cycle.