When people talk about improving their sleep, they usually start with the obvious: cutting screen time, upgrading their mattress, or popping a magnesium supplement. But few realize that the biggest lever they could pull - the foundation that underpins all sleep and recovery - is the circadian rhythm.
This week, we're diving deep into what your circadian rhythm is, how it governs your health and performance, and how you can harness it to sleep better, recover faster, and function at a consistently high level.
What Is the Circadian Rhythm?
At its core, your circadian rhythm is your internal body clock. It's a 24-hour cycle that regulates nearly every biological process in your body - from when you feel sleepy and when you wake up, to how your hormones fluctuate, how your metabolism fires, and even how your organs function.
The circadian system is controlled by the suprachiasmatic nucleus (SCN), a tiny cluster of neurons in the hypothalamus. This master clock receives direct input from your eyes and is especially sensitive to light - particularly blue light from the sun. That's why morning light exposure is so crucial: it tells your body, "Hey, it's daytime - let's get moving."
According to Dr. Peter Attia, author of Outlive, the circadian rhythm governs the timing of cellular repair, immune responses, and even athletic performance. "If you get this rhythm right," Attia says, "you unlock massive gains in everything else you're trying to do - longevity, strength, metabolism, even mental clarity."
Real-World Examples of Circadian Rhythms in Action
You know that groggy feeling you get after a red-eye flight? That's your circadian rhythm getting knocked off course. Jet lag, seasonal affective disorder, and even chronic insomnia can all be traced back to misalignment between your internal clock and your external environment.
On the flip side, you've probably noticed days when you're laser-focused in the morning and crash like clockwork around 3 p.m. - again, that's your circadian rhythm at work.
Elite athletes know this intuitively. Many of them schedule training and recovery around their body's peak performance windows. Pro marathoner Keira D'Amato, for instance, keeps her sleep and wake times consistent even while traveling, knowing that syncing her rhythm is essential for racing and for recovery.
I've seen it in my own life too. When I started sticking to a regular wake time (yes, even on weekends) and prioritized early morning sunlight, my sleep improved dramatically. Not just the quantity, but the quality. I started waking up more refreshed and falling asleep faster, even on high-stress days.
Why Circadian Alignment Changes the Game
The circadian rhythm isn't just a sleep timer, it's a master regulator. When it's out of sync, your melatonin production, cortisol spikes, appetite regulation, and temperature shifts all go haywire. That's when sleep issues show up… You might fall asleep easily but wake up groggy, or struggle with mid-night wakeups, or feel sluggish despite eight hours in bed.
"Sleep is not just about how long you sleep, but how aligned that sleep is with your circadian rhythm," says sleep scientist Dr. Matthew Walker, author of Why We Sleep.
This alignment (or misalignment) also affects athletic performance. Studies show that strength, flexibility, and anaerobic output peak in the late afternoon for most people. If you’re not aware of how your body feels at a specific time of day, you may not be optimized for performance. Knowing your body clock allows you to adjust - even when changing time zones - by strategically shifting your rhythms preemptively.
How to Know Where Your Rhythm Is At
You don't need a sleep lab to monitor your circadian rhythm. Here are a few practical indicators:
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Sleep Timing: When do you naturally feel sleepy and wake up, without alarms or stimulation?
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Energy Levels: Do you feel a surge of energy at predictable times? A crash?
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Body Temperature: Your body runs a little warmer during the day and cooler at night. Tools like the Oura Ring, WHOOP, and Garmin watches track this.
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Heart Rate and HRV: Elevated nighttime heart rate and reduced HRV can signal poor circadian alignment.
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Sleep Quality Scores: Tools like the COROS app, Fitbit, or Eight Sleep score your rest based on rhythm alignment and duration.
Some athletes go even deeper - for example, Dakotah Popehn shares her Oura data with her coach, who adjusts her training based on her HRV and sleep cycles. "If I'm not recovering well, we pull back," she says. "But if my rhythm is locked in, we can push a bit harder."
Can You Shift Your Circadian Rhythm?
The short answer: Yes - but with some caveats.
Dr. Andrew Huberman notes that the circadian rhythm is plastic but not infinitely flexible. You can shift it, usually by about 15-30 minutes per day, using timed light exposure and darkness. For example, if you're trying to shift your sleep earlier, exposing yourself to bright sunlight within 30-60 minutes of waking and avoiding bright light after 8 p.m. is key.
But Peter Attia makes an important distinction: "You can nudge your rhythm, but you can't totally override your chronotype. Some people are naturally morning larks, others are night owls. Rather than fight that, it might be better to optimize your schedule around your baseline."
In other words, if your body naturally wants to sleep from midnight to 8 a.m., trying to become a 5 a.m. riser might do more harm than good. Instead, protect the rhythm you already have. Use it as a framework.
Tips for Optimizing Circadian Health
Here's how you can tune your rhythm like a pro:
1. Anchor Your Wake Time
Waking at the same time every day is the single most powerful way to stabilize your rhythm. Even if you stay up late, keep your wake time the same and take a short nap if needed.
2. Get Morning Sunlight
This is the real cheat code. Go outside within 30-60 minutes of waking for at least 10 minutes. No sunglasses, no windows - just raw natural light. It signals your SCN that it's time to start the day.
3. Dim the Lights at Night
As bedtime approaches, mimic dusk. Use warm, dim lighting; turn off overheads; avoid screens; or use blue light blockers and night mode.
4. Time Your Exercise and Meals
Exercising too late can shift your rhythm forward. Same with eating. Try to work out and finish meals 2-3 hours before bed.
5. Control Your Sleep Environment
Cool room, quiet, and total darkness (or a sleep mask) - of course, with your perfect pillow. Make your bedroom a place your circadian system recognizes as the cue for rest.
6. Track and Adjust
Use wearable tech to monitor your rhythm over time. You'll start to spot trends—like how alcohol, late meals, or inconsistent sleep affect your recovery and performance.
7. Don't Panic About One Off Night
One bad night won't wreck your rhythm. What matters is consistency over weeks and months.
Putting It Into Action
Your circadian rhythm is your sleep's conductor. When it's dialed in, everything else - falling asleep, staying asleep, waking up refreshed, training harder - becomes easier. But ignore it, and no amount of supplements or fancy gadgets will get you back on track.
So start with the basics - set your wake time; get outside; create an evening wind-down routine; track how you feel; and optimize your environment.
And remember - if the world's top athletes build their routines around this rhythm, maybe it's time we all do the same.
