Resting heart rate and HRV by activity level and age
a (cross-sectional) look at the data
What is the relationship between resting physiology, activity level, and age, and how does this differ for resting heart rate and HRV?
In this data, physical activity level can explain only 5% of the variance in HRV, while aging explains 14%, i.e. HRV tracks well with aging, over decades, but not much with physical activity level.
For heart rate, there is no influence of aging (0% of the explained variance), and 10% of the explained variance is due to physical activity level, i.e. heart rate tracks quite well with changes in physical activity behavior / cardiorespiratory fitness, as we know from the scientific literature as well.
In the graph above, I've transformed HRV to logarithmic units (times 2, this is similar to the score you see in HRV4Training) as HRV is not normally distributed. This way it is easier to see that HRV tracks a bit with physical activity level, but not much (and maybe not beyond what can be explained just by a reduced resting heart rate?).
This makes HRV a poor outcome metric, as even quite different physical activity levels, resulting in very different resting heart rates, might result in the same or very similar HRV, for people of a given age group.
Still, HRV does reduce quite clearly with age, and in ways that are not reflected in heart rate data, hence possibly providing valuable information on the "health" of the autonomic nervous system: there is something in there that is clearly not captured by resting heart rate alone.
Different metrics, different uses.
As looking at reductions in HRV over fifty years might not be the most practical way to go about it, I consider HRV useful mostly in the context of managing stressors on a day-to-day basis, as a marker of our response to such stressors*, and not as an outcome metric (with exceptions, of course).
*keep in mind that to use HRV this way, protocols matter, and data must be acquired at rest, far from stressors, otherwise you are not assessing your response
Marco holds a PhD cum laude in applied machine learning, a M.Sc. cum laude in computer science engineering, and a M.Sc. cum laude in human movement sciences and high-performance coaching.
He has published more than 50 papers and patents at the intersection between physiology, health, technology, and human performance.
He is co-founder of HRV4Training, advisor at Oura, guest lecturer at VU Amsterdam, and editor for IEEE Pervasive Computing Magazine. He loves running.
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Twitter: @altini_marco.
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I am a Septuagenarian and my clades data doesn't even show up on that graph, which begs the question: what was the (original) source of that data? As an aside, I think it somewhat obvious that HRV would reduce with age given that atrial fib probabilities rise with it.
The very latest research has shown that fitness degradation with age is largely a myth when you remove confounding factors like arthritis.