The resting heart rate (RHR) can be used to evaluate one’s physical health. A low RHR is typically associated with a high life expectancy . The heart is a muscle like every other and therefore it can be trained. Intense training is beneficial to keep this muscle healthy and productive. A low RHR during inactivity gives it time to rest and thereby protects it in the meantime.
For healthy and active young people a typical RHR is in the order of 60 beats per minute, for inactive people it is usually higher. Many factors can influence the resting heart rate: sickness, stress or even caffeine cause temporary spikes. This means the current RHR is usually a good measure of your physical state right now. Measured and compared on the long term, it offers a good measure for the general state of your health: Fitness and weight reduction are known to lower the RHR and are therefore beneficial to increase your life (besides all the other benefits in terms of quality of life!).
Without intending to, I conducted a self-experiment in the last couple of month on the influence of exercise on my RHR: I collected my heart rate data with my Garmin Vivosmart HR+ which I wear every day and night. It calculates the resting heart rate mostly from my sleep data and averages them over a month. As a runner, I also collect my training data with an old Garmin Forerunner 220. (No, this is not a paid ad, I just like those Garmin products!).
Exercise lowers the resting heart rate…
I usually run about 3 times a week, independently of the weather, mostly for fun and the positive effect running has on my life. I am not an ambitious runner, but I attended a few running events such as half-marathons in the last couple of years.
At the beginning of 2019, I increased my training and running kilometers until I was in pretty good shape around May. After this I ran less in summer due to the heat. The effect of the training can nicely be seen in my RHR data, which decreased visibly until May:
The lower training intensity during summer can again be seen in the slow increase of RHR after May. Once I got used to running in the heat and increased my training again, the RHR reacted quickly reaching its minimum in September.
… no exercise increases it.
Beginning of September I made a stupid false move and injured my knee, leading to a running frequency decrease from 3 times per week to zero. Right after it happened I was barely able to walk. I could not get myself to try other kinds of exercise, so I barely moved at all. In December, I finally was able to get back on my feet and ran my first little training runs. The overall training break was about 3 months long.
The effect this had on my RHR is astonishing: From my minimum of 54 beats per minute in September when I was in good shape, my RHR rose up to 62 during the training break until December. This happened gradually over three months and can nicely be seen in the data.
The lesson is clear:
Many different factors influence the RHR, among them diet, weight and exercise. I did not change my lifestyle in the last year apart from the training intensity, which is why I attribute the visible change in RHR to the lack of exercise. This matches nicely with several scientific studies showing the correlation of (especially endurance) training on the RHR .
As a scientist with a passion for biohacking, this really fascinates me: I really did not expect to see an influence on my heart rate this fast. Of course other influences might also be involved in the change we can see in the data. But I felt the missing exercise also in many other aspects of my life: During inactivity, I was rapidly losing my compulsion to move – which I thought was part of who I am. While the first few weeks were horrible because I really missed running, I lost my drive eventually. I wouldn’t have thought that this is possible. Now that I am getting back into training, I can feel it coming back only slowly. Furthermore, I was less balanced and couldn’t handle stress well during the break.
I really value the positive effects exercise has on my life, which is why I am fighting my way back into an active life style right now – even if it is harder than expected!