Your energy moves in waves through the day: stretches of about 90 minutes of high alertness, alternating with dips of 20 to 30 minutes in which concentrating takes real effort. Kleitman called this the Basic Rest-Activity Cycle and saw it as the waking continuation of the sleep cycle, which also runs in blocks of roughly 90 minutes.
That link to the night does not hold up. Lavie measured daytime sleepiness rhythms in 1995 and found they are not anchored in the sleep stages: mornings have a different structure than afternoons, and the first dip arrives about 100 minutes after waking, whatever stage you woke from. The rhythm is real, but the clock of your night does not set it.
The 90 minutes is a rule of thumb, not a stopwatch. Huberman points out that you can start a cycle yourself, unlike your circadian rhythm, and that two or three of them fit in a day. Storoni works with 60 to 90 minutes, shorter as the day wears on. Among the 10 percent most productive people, DeskTime measured 112 minutes of work followed by a 26-minute break.
So put your hardest work in blocks of 60 to 90 minutes, with the most demanding part in the first twenty, and then take a real break instead of sliding into the next screen. Do not wait for the right moment in your rhythm, because you start the cycle yourself; the break is what makes it repeatable.
Related:
- Before you start (a task, a work session, a project…), set a time budget
- Avoid excessive task switching to increase efficiency
- A 5-minute unstructured break is enough to regain your focus
- Schedule two hours every day for important work that doesn’t need to be completed immediately; this helps you become happier and more productive
- Creative tasks are best done while low on energy
- Spend a little attention on planning and organizing your tasks, but not more than necessary; then, get to work
- Try to get four hours of concentrated work into a workday, and never more than six
- Allow small tasks to accumulate until you can efficiently complete them in batches
- In general, people perform better in the morning hours than later in the day
- Productivity doesn’t come from working longer, but from letting your brain reset