What is ultradian rhythms energy management?

Ultradian rhythms energy management is a concept in personal epistemology: Your energy cycles in 90-minute waves — work with these rhythms not against them.

Example: A software engineer notices she writes her best code in focused bursts that last about 90 minutes before her attention starts to fragment. She used to push through the fragmentation — forcing another 45 minutes of degraded work before finally breaking. After learning about ultradian rhythms, she restructures her day: 90 minutes of deep coding, then a 15-20 minute genuine break (walk, stretch, casual conversation — not email). She tracks her output for a month and discovers she produces more quality code in three 90-minute cycles with real breaks than she did in six hours of continuous desk time. The total clock hours are fewer. The total output is higher. The end-of-day exhaustion is lower. She did not become a better programmer. She became a better allocator of her existing capacity by working with her biology instead of against it.

This concept is part of Phase 36 (Energy Management) in the How to Think curriculum, which builds the epistemic infrastructure for energy management.