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Productivity methods and focus

Ultradian rhythm

A body rhythm that repeats more than once a day, such as the roughly 90-minute cycle of sleep stages, shorter than the 24-hour circadian cycle.

What It Means

An ultradian rhythm is a biological cycle that runs its course and starts again several times within one 24-hour day. The best-known human example is sleep: a night passes through repeating cycles of about 90 minutes. Kleitman, a sleep researcher, proposed that this cycle reflects a basic rest-activity cycle (BRAC) that keeps running while we're awake, and some people plan their workday in blocks of about 90 minutes around that idea.

Try It: Fit Focus Blocks Into Your Morning

Set the time you have, a focus block and a break. The starting numbers are an example, not a rule from the research.

Block length90
Full blocks that fit2
Focus minutes180
Minutes left over45

Use the leftover minutes for email and small jobs.

How People Say It

  • "I work in 90-minute sprints, then I get up."
  • "My brain always crashes about an hour and a half in."
  • "I'm riding the ultradian wave this morning."

The Breakdown

How to try it (Buhata's own suggestion)

  1. Pick one demanding task for your first block.
  2. Set a countdown for 90 minutes, or a shorter block if that's too long to start with.
  3. Work on that task alone until it ends.
  4. Take a real break of 1010,000 stepsA popular daily step goal that began as the name of a 1960s Japanese pedometer; later studies find health benefits begin well below it. See more to 20 minutes away from the screen.
  5. Note how the last 20 minutes of the block felt, and shorten or lengthen the next block to match.

Try it today. Use the planner above for tomorrow morning and put the hardest task in block one.

What the research does and doesn't show

FindingSource
Sleep runs in cycles of about 90 minutes"Neural and Homeostatic Regulation of REM Sleep"
Kleitman proposed a rest-activity cycle that might continue while awakeSame paper
Some studies report 1 to 2 hour cycles in waking body signalsBAT thermogenesis paper; task performance and EEG study
One study found no rest-activity cycle in movement at the head, wrist or ankle"No basic rest-activity cycle in head, wrist or ankle"

The sleep cycle is well established. A steady 90-minute cycle of alertness during the day is less certain, so treat the block length as a starting point you adjust.

Where It Comes From

Kleitman, who studied human sleep, looked at the roughly 90-minute sleep cycle and proposed that it was one sign of a basic rest-activity cycle running through the day as well as the night. Later studies have tested that idea with mixed results.

Good to Know

The 90-minute block is a planning habit borrowed from sleep research, and the waking evidence is mixed. If you nod off during the day or feel exhausted however you arrange your work, talk to a doctor, since sleepiness has many causes a timer won't fix.

FAQ

What is an example of an ultradian rhythm?

The sleep cycle. Through the night you pass through repeating cycles of about 90 minutes, as described in research on REM sleep published in PubMed Central.

Should I work in 90-minute blocks?

You can try it, but it's a suggestion rather than a proven rule. Research on waking rest-activity cycles is mixed, so adjust the length to what keeps you focused.

What's the difference between circadian and ultradian rhythms?

A circadian rhythmCircadian rhythmThe body's roughly 24-hour cycle of physical, mental and behavioral changes, such as sleepiness at night, kept in time by a clock in the brain that follows light. See more takes about 24 hours, like the daily pattern of sleepiness at night. An ultradian rhythm is shorter and repeats several times a day, like the sleep cycle.

Do It in Buhata

Focus and Tasks

Run each block as a countdown in Focus in Buhata and add the next block's task to Tasks before your break starts.

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Related Terms and Categories

  • Circadian rhythm

    The body's roughly 24-hour cycle of physical, mental and behavioral changes, such as sleepiness at night, kept in time by a clock in the brain that follows light.

  • Chronotype

    A person's natural lean toward earlier or later times for sleeping and being active, usually described as morning, evening or in between.

  • Pomodoro technique

    A focus method that splits work into 25-minute rounds separated by short breaks, with a longer break after every four rounds.

  • Deep work

    Focused, distraction-free time spent on a mentally demanding task, a term from author Cal Newport's 2016 book Deep Work.

Productivity methods and focus

Sources

"Neural and Homeostatic Regulation of REM Sleep" (PubMed Central); "Brown adipose tissue (BAT) thermogenesis heats brain and body as part of the brain-coordinated ultradian basic rest-activity cycle (BRAC)" (PubMed Central); "Ultradian rhythms in task performance, self-evaluation, and EEG activity" (PubMed); "No basic rest-activity cycle in head, wrist or ankle" (PubMed)

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