Fitbit research quantifies link between physical activity & resting heart rate

New research published in a Fitbit blog post confirms the link between increased physical activity and improved resting heart rate (RHR), heart rate variability values (HRV) and Sleep Scores. The data also shows how much physical activity is required for results to show.

It is a well known fact that the average person is not active enough. Official guidelines recommend at least 8,000 steps per day. For even greater health benefits a healthy person should aim for 150 minutes a week of moderate-intensity activity, or about a half of that amount of vigorous-intensity activity. These figures come from to the American Heart Association.

Essential reading: Top fitness trackers and health gadgets

For step count, in this research Fitbit looked at slightly a slightly higher target – 10,000 steps per day. As far as exercise the company has an Active Zone Minutes (AZM) metric which is a good approximation of the American Heart Association guideline for the weekly exercise target. AZM awards points depending on how hard your heart pumped during exercise. 150 AZMs are roughly equivalent to the 150 minute per week moderate-intensity goal. Nice and simple.

What does the data show?

Fitbit’s anonymised data for this research includes some 471 million AZMs and 106 billion steps. Users were challenged to meet their physical activity targets during February of 2022. A good month as the January hype from New Year resolutions would have passed.

During February, those that consistently met both 10,000 steps per day goal and 150 AZMs per week saw:

• A decline in their RHR by 8.1% on average or 4 bpm (beats per minute);
• Growth in HRV by 20% or 6.1 milliseconds (higher figures are better);
• Stress Score improved by 7.3% or a 5.4 difference.

Positive results started showing in as little as two weeks of consistently meeting these targets. In that period, heart rate variability grew by 20%, RHR fell by 4.3% and Sleep Scores improved by 4.2%.

It would be logical to assume that if a person stuck to these targets beyond the first month, health benefits would be even larger. The research shows that these positive effects on health lasted for over 4 weeks even if activity levels later dropped.

Some of the people under observation only met the 10,000 steps per day goal. This also gave a boost to their health, but not as much as for those that met both targets.

More specifically, during the month these individuals saw:

• A decline in their RHR by 3.05 bpm;
• Growth in HRV of 3.44 ms;
• Stress Score improvement of 3.97.

Finally, there are also those who only managed to consistently meet the 150 AZMs per week recommendation. Their improvements came in at:

• 1.35 bpm lower RHR;
• 3.08ms higher HRV;
• 5.08 higher Stress Score.

All this shows that for maximum health benefits you should aim to hit both the daily step count and moderate weekly intense activity score. Failing that, meeting either of these targets will improve your wellbeing. And these health benefits will continue for a while, even if your activity levels drop.

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