Heart Rate Variability (HRV) and training load

Blog post by Marco Altini
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It is a common misconception that HRV should track training load, reducing when training load is higher.

In particular, studies looking at the relationship between HRV (and other metrics) with training load over time, look at how these metrics correlate. However, the whole assumption that you should find the metric that “correlates the most” with training load, makes very little sense.

Why? Because you are already measuring training load. What is the point of having another metric that gives you the exact same information? By definition, if a metric is perfectly correlated to training load (positively or negatively), then it is a useless metric.

If HRV had a perfectly negative correlation with training load, It would not add any information to the training and recovery equation. Ironically, these studies would interpret the metric with the highest negative correlation with training load as the best metric (!).

On top of this, HRV is all about individual responses. A non-relationship at the group level does not tell us anything at the individual level. Maybe a few people responded very well and had increased HRV. Other people had a suppression in response to the same load. This is exactly why we monitor.

It makes sense to analyze group-level data in response to acute stressors (see for example our paper here where we look at training, sickness, alcohol intake and the menstrual cycle) However, in the long run, acute and chronic responses differ. As such, a group level analysis does not tell us anything about the individual response.

The notion that increased load should trigger a reduction in HRV is very simplistic. We can have stable or increased HRV when increasing load (a sign of positive adaptation) and decreased HRV with reduced load because of other stressors (travel, work). Check out this blog for more information on HRV trends.

How should we use HRV and training load information then?

If our training load is increasing and our HRV stays within normal or increases, that’s great, it means we are responding well to stress. This is confirmation that we can take the load, maybe even increase it a little more. In general, HRV should not negatively correlate with load.

​By measuring your resting physiology first thing in the morning, you can understand how you are responding to training (and other stressors), and use that information as part of your decision-making process.

If you are coping well with stress, HRV will not be decreased.

For more misconceptions about HRV tracking, check out Part 4 of my Ultimate Guide To Heart Rate Variability.