Ultradian Rhythms

Ultradian rhythms are biological cycles of roughly 90–120 minutes that govern periods of high and low cognitive alertness throughout the day. Unlike circadian rhythms, which regulate the sleep-wake cycle over 24 hours, ultradian rhythms create multiple peaks and troughs within waking hours. Working with these rhythms — concentrating deep work during peak periods and resting during troughs — produces more output with less fatigue than forcing continuous effort. The model reframes productivity as a wave, not a line: sustained high performance requires alternating between intense focus and genuine recovery, not grinding through a flat, undifferentiated workday.

Structure your day around 90-minute work cycles. Schedule your most demanding cognitive work — strategic thinking, writing, complex problem-solving — during your first ultradian peak (typically the first 90 minutes after your morning routine). Follow each cycle with a genuine 15–20 minute break: walk, breathe, rest your eyes. Track your energy peaks and troughs for a week to identify your personal rhythm. Defend peak periods from meetings and reactive work.

Ultradian rhythms are 90–120 minute cycles of high and low alertness. Working with them — deep focus during peaks, rest during troughs — produces more and better output than continuous effort.