We’ve all heard of circadian rhythms.
The natural 24-hour cycles that govern our sleep and wake patterns.
It’s the backdrop of how we live even if we don’t always realize it.
I’ve learned that there are also cycles that live within this day/night cycle.
These can be the keys to helping us live with our most energy and creativity.
Nighttime Cycles
Over a decade ago, I learned something that changed how I sleep.
We don’t sleep in one solid block.
We go through 90-minute patterns that are known as ultradian rhythms.
These cycles include light sleep, deep sleep, and REM.
And these patterns repeat 4 to 6 times a night.
Once I started noticing these 90-minute windows, I began to work with them.
If I woke up in the morning between cycles, I’d get up.
If I had time, I’d lie back down for another full cycle, not just “15 more minutes.”
Over time, I started to feel the difference.
There’s even a name for that groggy fog we feel when we’re woken mid-cycle: sleep inertia.
It can take your brain 30 minutes or more to come back online.
Daytime Cycles
Then, I heard something else that clicked.
Those same 90-minute ultradian rhythms don’t stop when we wake up.
They continue during the day.
Sleep researcher Nathaniel Kleitman called it the Basic Rest-Activity Cycle (or BRAC).
While asleep, it moves us through the stages of sleep.
While awake, it shows up as periods of high focus and energy.
Followed by dips in clarity, motivation, or alertness.
The Pomodoro technique, which I’ve used for years, maps surprisingly well to this.
Short bursts of focused work (25 minutes), then a break (5 minutes).
After 4 focus sessions, the break is longer.
We’re wired for these rhythms.
With daily hustle and constant output, we aren’t honoring the natural rhythms.
As a result, we aren’t delivering at our best.
What This Means for Our Days
We need to start paying attention to our energy, not just our time.
Determining when we are the most creative, the most focused.
And when we feel foggy or distracted and need some rest.
Remember the cycle 90-120 minutes of focus and then 15-30 minutes of rest.
A walk, sunlight, stillness, or catching up with a friend.
We need to shift our mindset.
These moments aren’t slacking they are syncing with our natural rhythms.
Allowing us to show up at our best.
Your Turn
Have you noticed your own 90-minute patterns during sleep or at work?
What does your energy arc look like throughout the day?
What would change if you stopped managing minutes and started managing ultradian rhythms?