Can heart rate variability (HRV) be accurately used to gauge daily readiness for physical activity?

This is a very valid question I have received recently on X, after I had highlighted how absolute values of HRV tell us very little about our health. Below are some of my thoughts.

I wouldn't say readiness to train can be provided with HRV alone, as HRV is missing key aspects of "physical activity readiness", e.g. muscle soreness.

However, if you use HRV together with a training plan, where you have periodized your training, then you can use HRV to assess how you are responding (e.g. is it too much, are there other stressors causing a poor response, etc.) and potentially, to make adjustments (e.g. reduce training intensity stimulus or prioritize other forms of recovery, like sleep).

I consider HRV useful as an overall marker of stress (training, life, environment, etc.), and of our capacity to handle stress in a given moment, provided it is measured according to best practices. It is probably more about what we can absorb and benefit from, more than what we can do (we can often perform on a low HRV, but we might not turn that stimulus into higher fitness, which is irrelevant on race day, but a key aspect of the training process, hence once again, what we do - or can do or should do - does not depend on HRV alone, but HRV and context).

This way, it becomes useful feedback, and actionable, but it is not really about absolute values, nor it is useful when automatically measured and included in "readiness or recovery" scores which lack context and subjective feel, or other key - but unmeasurable via a wearable - parameters (e.g. muscle soreness).

HRV measured with a good protocol, plus subjective feel (soreness, motivation, etc.) and additional context (load, non-training related stressors), gives us something to work with that can be helpful, in my opinion.

You can see an example of my own data below, the protocol is a morning measurement after waking up, sitting, using HRV4Training, and then I add subjective feel (via a questionnaire) and context (training, travel, etc.).

The visualization is part of HRV4Training Pro.

If you already use the HRV4Training app, you can try Pro here.

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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.

Social:

• Twitter: @altini_marco.

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