Ultradian rhythm explained
Physiologist Nathaniel Kleitman proposed a basic rest-activity cycle of about 90 minutes that continues through the day as well as during sleep. The sleep cycle is well established; the daytime version has mixed evidence.
Even so, 60 to 90-minute focus blocks followed by a real break are a practical, low-risk way to structure deep work.
Try it today
- Work for 75 to 90 minutes on one task.
- Take a 15 to 20-minute break away from screens.
- Notice when your focus naturally fades and plan around it.
Where it comes from
Nathaniel Kleitman proposed the basic rest-activity cycle. Researchers have since disputed how strongly it applies while awake.
Frequently asked questions
- What is an ultradian rhythm?
- An ultradian rhythm is a body cycle shorter than a day. In productivity, it usually refers to the idea that alertness rises and falls in roughly 90-minute waves, so work in 90-minute blocks with breaks.
- Where does an ultradian rhythm come from?
- Nathaniel Kleitman proposed the basic rest-activity cycle. Researchers have since disputed how strongly it applies while awake.
- How do I start with an ultradian rhythm?
- Work for 75 to 90 minutes on one task. Take a 15 to 20-minute break away from screens. Notice when your focus naturally fades and plan around it.
- Which tools help with an ultradian rhythm?
- Tools in our directory that help include Focusmate, Google Calendar, Orb. Each has its own page with pricing, pros and cons.