[101] Infradian Rhythm

An intro to the 'other' circadian clock that beats the rhythm to female biology

Let’s talk chronobiology! This word is buzzinnn' in the world of biohacking, and thanks to that, dorky things like blue-blocking eye-wear are becoming cool.

Much of this chronobiological fanfare is in the context of optimizing the circadian rhythm, which as you know, is the 24-hour clock that rules our biological processes (everything from sleep, digestion, healing & recovery...).

But, have you heard of the other chronobiological drumbeat that, for some of us, may be even more important to pay attention to than the good ol' 24-hour beat?

**drum roll please**

enter. the. infradian. rhythm.

OK, quick etymology tangent! circa means “about”; dia means “day”; together circa-dia describes a process that occurs in the period of “about a day” (aka. its pattern of recurrence is daily).

So, what about infradian? infra means “below”; so, infra-dia means “below a day”... in other words, it describes a pattern with lower frequency than daily (aka. occurs less frequently than on a daily basis), so the process takes longer than 24 hours.

What do womxn(1) experience with regularity roughly every 28 days?

You guessed it, menstruation.

On the most basic surface level, we can understand the infradian rhythm as the 28-day(2) clock that regulates the menstrual cycle through its four phases (menstruation, the follicular phase, ovulation, and the luteal phase). You may have learned at some point in Bio class that what changes throughout the monthly cycle is the balance of sex hormones.

But, if we take a closer look, we start to see how this monthly rhythm affects more than just our reproductive system. Alisa Vitti(3) explains how several other biological processes are tick-tocking along the 28-day rhythm:

  • Brain neurochemistry: the infradian rhythm creates a 25% change in brain chemistry over the course of the month

  • Metabolism: speeds up and slows down predictably over the cycle

  • Stress response: cortisol levels shift throughout the cycle, hitting a peak during a specific phase

  • & more: hormonal fluctuations influence body temperature, skin elasticity, sleep, energy, immune system, microbiome, et al.

Still unsure why you should care about the infradian rhythm? These are some of my personal reasons, which may resonate with you:

  • As someone who cares about being my best version of self and optimizing my day-to-day health and productivity, the infradian rhythm gives me a more holistic paradigm through which I can achieve those goals

    • side note: even those that do not identify as womxn would also benefit from learning about this topic and become a more aware partner / brother / father / friend / etc.

  • (At the expense of stating the obvious,) any hormonal imbalance or reproductive health issue (PMS, PCOS, endometriosis, infertility, libido, etc.) is best addressed in the context of the infradian clock

  • Any weightloss or muscle-building body-recomposition plan is likely to feel easier and less stressful when synchronized to the infradian rhythm

  • It's undeniable that hormones affect so much of what we experience as 'life' (the compilation of physiological and psychological phenomena), so learning about the infradian rhythm and how to best work with it, is empowering

artwork by @danica.gim. website: Danica Gim

Instead of feeling confused (at best) and burdened (at worst) by our menstrual cycles and fighting against the clock, we can familiarize ourselves with it and learn to work with it.

What are some concrete examples of applying this knowledge of the infradian rhythm in our lives?

  • Capturing synergies by syncing diet and exercise to the infradian rhythm lets us optimize our metabolism and leave the hamster wheel of “dieting” for good

  • Being mindful of planning activities around phases of the cycle (i.e. there are different phases where we are better suited for planning or brainstorming; social engagements or networking; high intensity exercise; fasting; nesting, resting, and self-care; etc.) lets us increasing productivity at home and at work

  • Paying attention to the infradian rhythm lets us ensure we are managing our energy and stress levels: controlling blood sugar by syncing our diet to phases of the cycle; avoiding scheduling stress-inducing events during the peak cortisol production phase;

Stay tuned for more posts on the infradian rhythm with cycle-syncing tips and tricks!



(1) Describing all those with female physiology in reproductive years. (2) 28 days being the average; according to medical experts a normal cycle can last anywhere from 21 to 35 days. (3) Alisa Vitti, HHC, AADP, is an integrative nutritionist, hormone expert, author, and founder of FloLiving.