Training Adaptation and Heart Rate Variability in Elite Endurance Athletes
by George Blackwell
The research I’m reviewing for this week’s newsletter is actually nearly 10 years old, but is more relevant than ever today. Measurements for HRV are becoming more and more accessible as Garmin and other wearables (like Whoop and Oura) have been putting such an emphasis on ‘Readiness to Train’ based off HRV.
© Garmin
Dr Dan Plews, a very well established exercise physiologist and endurance coach, has worked closely with athletes who have won more than 25 World and Olympic titles across multiple different sports including rowing, sailing and triathlon. He’s published 15 papers and has been cited thousands of times on the topic of HRV.
His research shows us a few key trends that you can take into account if you’re currently monitoring your HRV on a longer-term basis. Here they are.
HRV in Response to Different Training Loads
In moderately trained subjects, moderate training loads increase aerobic fitness as well as HRV. However, when training loads are close to 100% of an individual’s maximum tolerable training load, HRV becomes suppressed. This is thought to rebound after a period of reduced training (i.e., a taper period).
For example, after 3 weeks of overload training in swimmers and distance runners, HRV was reduced by 22% and 38% respectively. It then rebounded and increased by 7% in the swimmers and 38% in the distance runners following a 2-week period of reduced training load.
HRV and Positive Adaptation to Training
In sedentary and recreationally trained individuals, endurance training for 2, 6, and 9 weeks has been shown to create parallel increases in aerobic fitness and HRV. In other words, as you get fitter, HRV will increase in a linear fashion. However, despite this being the typical response shown in sedentary and recreationally trained individuals, the response in athletes that have extensive training histories can be very different. In highly trained athletes, you can see an increase in HRV but no change in performance measures, and other studies see a decrease in HRV despite increases in physical performance.
HRV and Negative Adaptation to Training
The research provides less clarity on the relationship between non-functional overreaching (overtraining) and HRV. Overtraining is associated with reductions in performance ability that do not resume for several weeks or months. To date however, studies have examined changes in HRV with overtraining and revealed increases, decreases, and no changes reported whatsoever. It appears the inconsistent findings shown between HRV and overtraining are likely due to the methodological approach adopted and the type and extent of overtraining induced. However, further research is needed to clarify.
The paper concludes with a statement that longitudinal monitoring is required to understand each athlete’s optimal HRV and the trends that are seen with good / poor performance in both training and competition.
In the case of elite or highly trained athletes, increasing HRV values as competition approaches may be a sign of positive adaptation or coping with training load. Reductions in HRV in the week/days before pinnacle events may represent increasing freshness and readiness to perform. Further research is needed to confirm this initial finding and gain a clearer understanding of how changes in HRV relate to training intensity distribution, as well as to describe further the HRV trends for elite athletes leading into major competitions.
References:
Plews, D.J., Laursen, P.B., Stanley, J., Kilding, A.E. and Buchheit, M., 2013. Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring. Sports medicine, 43, pp.773-781.