Your brain runs on 90‑minute waves, learn to surf them

Across a normal day, physiology rises and falls in a repeating 90–120 minute pattern known as an ultradian rhythm. Heart rate, muscle tension, and brainwave activity ramp up, then ease off, and so does your attention. Early sleep researchers described a similar wave at night. Later work showed the same daytime oscillation. The implication is practical: peak focus isn’t a straight line. It’s a tide.

When people ignore these dips, performance doesn’t just flatten, it degrades. Errors climb, reactivity rises, and the brain reaches for stimulants. NASA’s fatigue program found that short naps improved alertness by up to 100% in high‑demand roles. On the sports side, top competitors recover between points with precise routines, dropping heart rates quickly so they can surge again. The pattern is universal: spend, then renew.

In workplaces, you can’t always nap, but you can use brief physical resets. A hospital team we observed added two 12‑minute blocks to long shifts. They walked stairs, refilled water, and practiced a simple 3‑in/6‑out breath. Nurses reported fewer charting errors and less end‑of‑shift irritability. One said, smiling over a cooling cup of tea, “I stopped snapping at people at 4 p.m.”

Mechanistically, breaks clear adenosine, regulate CO₂/O₂ balance, and tone the vagus nerve through longer exhales, which quiets arousal. You’re not being lazy, you’re keeping your system rhythmic so it can hit high notes on demand. Think of it as surfing: you paddle hard, ride the wave, then reset before the next set rolls in.

Put two alarms into your day at 90–120 minute marks and, when they chime, step away for a three‑part reset—move your body, refill your water, and breathe 3 in/6 out for ten cycles. If your environment allows, keep a 10–20 minute micro‑nap option just after lunch, using a second alarm so you don’t drift too long. Pick a consistent, screen‑free spot so the routine runs on autopilot. You’ll feel the difference later in the afternoon when most people fade. Try the first alarm tomorrow morning.