In a post on Zapier, Stephen Altrogge says:
"With the 90-minute focus technique, you take full advantage of the energy peaks and troughs that occur throughout your day: Work 90 minutes and then rest for 20–30 minutes.
Working in 90-minute bursts allows you to correlate your maximum energy levels with your task list, which then gives your productivity a major boost. You're working with your body instead of against it."
Tony Schwartz, wrote his book, "The Way We're Working Isn't Working: The Four Forgotten Needs That Energize Great Performance" in under six months by carving his workday into a trio of 90-minute chunks. He wrote no more than four and a half hours a day, and finished the book in less than 6 months.
Schwartz explains the 90 minutes cycle:
More than 50 years ago, the pioneering sleep researcher Nathan Kleitman discovered something he named the "basic rest-activity cycle" — the 90 minute periods at night during which we move progressively through five stages of sleep, from light to deep, and then out again.
Although it's much less well known, Kleitman also observed that our bodies operate by the same 90 minute rhythm during the day.
When we're awake, the movement is from higher to lower alertness. Other researchers have called this our "ultradian rhythm."
In his book, Schwartz writes:
"While working on The Last Supper, Leonardo da Vinci regularly took off from painting for several hours at a time and seemed to be daydreaming aimlessly. Urged by his patron, the prior of Santa Maria delle Grazie, to work more continuously, da Vinci is reported to have replied, immodestly but accurately, 'The greatest geniuses accomplish more when they work less."
In his renowned 1993 study of young violinists, performance researcher Anders Ericsson found that the best ones all practiced the same way:
- They practiced in the morning
- They practiced for three sessions
- Each sessions was 90 minutes or less
- There was a break between each session
That same pattern is found in other top performers, Schwartz reports: focus then rest, focus then rest.