Ultradian 90/20 is a preset with 90 min of focus, a 20 min short break, and a 30 min long break. You take a long break after every 1 focus sessions.
This is based on research showing that human alertness rises and falls in roughly 90‑minute cycles (the ultradian rhythm). After 90 minutes of focus, you rest for a full 20 minutes to make the most of one complete cycle. Because each session is long, even a single cycle can produce major progress.
It's well suited to work with high context‑switching costs, like deep research, papers, or large projects. But since 90 minutes is long, it's important to firmly block out distractions before you begin.