Haraldsdottir, K., Brickson, S., Sanfilippo, J., Dunn, W., Watson, A. In season changes in heart rate recovery are inversely related to time to exhaustion but not aerobic capacity in rowers. Scandinavian Journal of Medical Sports Science. 2017;00: 1-7
Link to abstract here.
What is heart rate recovery and why is it important? Heart rate recovery (HRR) is the difference between an individual’s heart rate at the immediate end of exercise and sometime afterwards, usually 30 seconds to one-minute post exercise. HRR is directly influenced by parasympathetic stimulation and sympathetic withdrawal, meaning that theoretically, a measure of HRR can be used to help determine cardiovascular training adaptations, as well as be used as a baseline measure for general health and fitness, two things that can exert influence on the autonomic nervous system. Within the body of research, most studies looking at athletes and their relationship to HRR following training has predominantly focused on cyclists and the results have been mixed, with several studies demonstrating HRR can be a marker for adaptation in either direction, depending on the intensity and type of exercise protocol used. This particular study looks at in-season changes in aerobic fitness and performance and their relationship to HRR in collegiate female rowers.
The testing protocol used was a step test, three-minute intervals at increasing intensity to failure. According to the protocol given, there was no rest allowed, so exercise was continuous. The testing was done prior to and immediately following the racing season.
So, the good stuff now. The study found that time to exhaustion increased over the course of the year, but HRR was actually negatively correlated with this stat. In addition, HRR does not seem to reflect aerobic capacity changes during the course of the competitive season; this is partially due to the fact that the VO2max for the rowers actually decreased slightly over the course of the season. This is not a surprising thing, given that during the competitive season, the type of racing is going to have a greater anaerobic emphasis, which would demand greater lactate transport and anaerobic threshold type training during the season than the aerobic training. You throw tapers, travel, and weekly racing and the aerobic capacity of most rowing athletes will decrease a bit. It should be noted that the study did not look at lactate levels, stress, or hydration levels so we can’t know for sure based on the study, but that would be my idea as to why this relationship between HRR, VO2max, and Time to Exhaustion exists.
In addition, training load was not accounted for during the course of the study or prior to the study, so again, I can only speak anecdotally from my time with rowing and the changes I know that occur during the season with training plans. The study did conclude though that HRR should not be used as an indicator for aerobic fitness, as they hypothesized it might, due to this seemingly inverse relationship they found between HRR and performance.