Heart Rate Variability (HRV) and Tapering

In this blog, I’d like to cover a common misconception about HRV and tapering, i.e., that your HRV should increase as you reduce training load before a race.

In particular, context here matters (as always!), and I’d like to consider two typical cases, also pertinent to how we can use HRV to assess our response to training:

Case 1: We’ve dug a huge hole with training, struggled, went way too deep, and now we really need a month-long taper to get back into somewhat decent conditions.

Case 2: We’ve accounted for recovery on a weekly (or at least microcycle) basis, trained long and hard, but never went too deep.

You can imagine which way I consider good training and which one not so much. These two approaches typically lead to different HRV profiles in the weeks leading up to the race.

In case of overdoing it in training, we tend to have a suppressed HRV, and then we do hope things somewhat re-normalize by the time we race. This makes sense as the load was already having a strong impact on the athlete’s physiology, possibly to a point at which a negative response was already reached. Keep in mind that a reduced HRV doesn’t mean we are training hard; it means we aren’t recovering well and aren’t assimilating the stress we impose on the body, typically leading to reduced performance. This is the case often shown in research when abnormally high training loads are imposed for the purpose of “overloading” the athlete (Flatt et al, Le Meur et al, Iellamo et al.).

It is important to highlight, however, that reduced HRV during increased load is not the response we normally target or hope to see. Increased load, when coping well with training and responding positively, should result in a stable or increased HRV. As a matter of fact, functional overreaching is associated with increased HRV, despite high load (Le Meur et al). After this increase, things change as we taper. Recent studies (Plews et al., Bellenger et al.) have indeed shown reduced HRV with reduced load during tapering. Notably, this reduction in HRV was associated with world-class performance, highlighting how the reduction was not detrimental to performance. Keep in mind that Case 2 above can include situations in which we do big training blocks and try to get to a state of functional overreaching, but we do so while monitoring the athlete’s response (subjective feel, physiological data, etc.) and making adjustments to make sure we are not spiraling into a poor response and ending up with Case 1 (if you don’t know how to navigate that line, get a good coach!).

In terms of the reasons behind the HRV decrease during taper, one could be the reduction in training volume, which might elicit lower blood plasma volume, and therefore decreased stroke volume, and in turn, increase heart rate and reduced HRV (Plews et al.). Another reason for HRV to reduce could be associated with an overly parasympathetic system during the previous periods of high load.