04/12/2025
You’ve probably heard this lately: “Men run on a 24-hour cycle, women run on a 28-day cycle.”
But… what’s the science behind that? Swipe through to find out.
The truth is: your body doesn’t run on just one clock. It runs on many.
In fact, we all have multiple internal and external rhythms that shape everything from our mood, to our hormones, to our energy, to our sleep.
Here’s a breakdown of six major biological clocks your body is syncing with every day:
🕑 Ultradian Rhythms
These cycles repeat multiple times per day - longer than an hour, shorter than a day.
One example is 90-minute cortisol pulses that affect energy, focus, and stress response.
🌅 Circadian Rhythm
Your master 24-hour clock regulating sleep, hormone release, body temperature, digestion, and more.
Fun fact: women tend to secrete melatonin earlier than men, which affects sleep timing.
📅 Infradian Rhythms
These last longer than 24 hours.
The most famous and impactful one? The menstrual cycle!
Men do also have infradian rhythms, like subtle ~4-day fluctuations in testosterone.
🌕 Circalunar Rhythms
A ~29.5-day rhythm tied to the moon cycle.
Common in marine life. Some female humans experience this but it’s less common today because of modern light exposure. Not something you need to aspire to sync with.
🌱 Seasonal Rhythms
Yearly patterns driven by shifts in light and temperature.
These affect mood, hormones, sleep, and even our habits.
Fun fact: The four phases of the menstrual cycle mirror seasonal patterns, too.
📆 Circannual Rhythms
Your internal year-long clock—shaped by the seasons and environmental cues.
So yes, the 24-hour vs. 28-day idea definitely has some truth…
But your biology is far more layered, dynamic, and beautifully complex.
Multiple clocks - all working together - shape how you feel throughout the day, month, and year.
Is this as fascinating to you as it is to me?
If you’re looking for sleep, mood and overall hormone support, the Fix Your Period Collective has got you covered this season! Your first step: my Period Quiz. fixyourperiod.com
