How Your Female Sex Hormones Affect HRV

Why your recovery scores may not be what they seem depending on your cycle.

Many women tell me that they use heart rate variability (HRV)—the variance in time between beats of your heart—for tracking recovery. HRV is the metric that Whoop Strap, Oura Ring, and other recovery tracking devices use to tell you how rested or ready you are. It’s a good indicator, but, like many physiological factors, female hormones affect it, so that number is not telling you the whole story—and sometimes it’s telling a false story. 

Your HRV is the result of the interplay between the parasympathetic (rest-and-digest) and sympathetic (fight-or-flight) branches of your autonomic nervous system. It describes the variability in the time between your heartbeats. When your HRV increases, that means your body is resilient to stress. When it decreases, you have less stress resilience.

Sounds straightforward—until you factor in sex hormones. Estrogen tends to increase vagal tone (i.e., the ability of your ventral vagal nerve to regulate your heartbeat), which is what devices measure to give you HRV. Progesterone, though “calming” in the brain, has the opposite effect on the vagal nerve and overrides estrogen’s effect on increasing vagal tone. In naturally cycling women, when progesterone goes up, estrogen is still there, but progesterone is the dominant hormone, decreasing vagal tone. When progesterone drops, estrogen becomes the dominant hormone, which increases vagal tone.

What Happens to HRV During the Menstrual Cycle?

In premenopausal women, HRV is influenced by the menstrual cycle. In the low hormone (follicular) phase, HRV is highest. After ovulation, as progesterone rises, it stimulates the sympathetic nervous system, which in turn increases resting heart rate and respiratory rate while reducing HRV.

What does all this mean? For one, your recovery metrics in the late luteal phase will always be lower as compared to the follicular phase because of those changes in the autonomic nervous system and how they affect HRV. So, you may be recovered, but because the devices are not based on an algorithm that understands hormone fluctuations, you may get a false low-recovery score, telling you that you are not fully recovered when you are. (You’ll note that what your device tells you and how you feel do not always match up) 

Of course, many women do experience lower recovery during the late luteal phase because of these and other physiologic changes. You can work with your physiology during this time to help counter these effects by addressing the systemic inflammation (which also impacts your recovery scores) that comes with the peak and drop of sex hormones right before your period starts.

I recommend using 1g of omega 3 fatty acids (DHA and EPA), which helps counter the inflammatory cytokine prostaglandin E2, which is increased by estrogen. Make sure you’re getting enough magnesium and zinc. And if you tolerate aspirin, take one 80mg baby aspirin to counter the inflammatory receptor sites Cox-1 and Cox2 and keep those receptor sites muted.

How Do Oral Contraceptives Affect HRV?

A paper I recently published looked at recovery responses across the natural and hormonal contraception (HC) driven menstrual cycles. We know that HRV is higher in the low hormone phase, and decreases as estrogen and progesterone increase across the natural cycle. But what is interesting is the patterns of recovery for women using HC. In the first few days of starting HC, HRV was elevated, but it significantly decreased across the active pill weeks, finding its lowest point in the first two days of the placebo pill; before increasing again. 

Why? Because when we are taking exogenous hormones, it takes a few days for the hormone levels to build up, and subsequent ingestion influences the vagal nerve; when the active pill and withdrawal bleed start, those exogenous hormones drop, reducing their influence over the vagal nerve. How does this fit into training when you are using HC? The body is most resilient to stress and high loads in the first 5 days of pill use, then gradually becomes less resilient (needs more recovery between hard sessions) until the last 5 placebo pills when the body is primed to take on stress again. 

What Happens to HRV During the Menopause Transition?

In perimenopausal women, the hormone ratios are completely different, and in postmenopausal women, they are flatlined, so the hormonal influences on the vagal nerve are altered. In both cases, you end up with more fight-or-flight activity and less rest-and-digest activity, especially after menopause.

There is minimal research on active women in the peri and post-menopausal phases of their lives; however, it is known that HRV decreases in the menopause transition and a new baseline is established in post-menopause. When we look at how this physiological decrease can affect recovery and recovery scores; we know that the current algorithms of wearables do not detect this change and cannot accurately predict true recovery. What we can do is monitor our trends in HRV, respiratory rate, and sleep quality. When you see lower HRV and higher respiratory rate (especially along with lower quality sleep) it’s time to back off. 

To increase your HRV you need to step in and activate those parasympathetic responses with changes to your lifestyle and behavior. Practice good sleep hygiene. Getting enough essential amino acids (EAAs) can help reduce central fatigue. Reduce your consumption of alcohol (which can reduce your HRV). Mindfulness and breathwork, exercising in nature, and a bit of cold water exposure are also strong vagus nerve stimulants.