Monitoring athletic training status using the maximal rate of heart rate increase

Objectives: Reductions in maximal rate of heart rate increase (rHRI) correlate with performance reductions when training load is increased. This study evaluated whether rHRI tracked performance changes across a range of training states. Design: Prospective intervention. Methods: rHRI was assessed during five min of cycling at 100 W (rHRI(cyc)) and running at 8 km/h (rHRI(run)) in 13 male triathletes following two weeks of light-training (LT), two weeks of heavy-training (HT) and a two-day recovery period (RP). A five min cycling time-trial assessed performance and peak oxygen consumption ((V) over dotO(2peak)). Results: Performance likely decreased following HT (Effect size +/- 90% confidence interval = -0.18 +/- 0.09), then very likely increased following RP (0.32 +/- 0.14). rHRI(cyc) very likely decreased (-0.48 +/- 0.24), and rHRI(run) possibly decreased (-0.33 +/- 0.48), following HT. Changes in both measures were unclear following RP. Steady-state HR was almost certainly lower (-0.81 +/- 0.31) during rHRI(cyc) than rHRI(run) A large correlation was found between reductions in performance and rHRI(run) (r +/- 90%; CI = 0.65 +/- 0.34) from LT to HT, but was unclear for rHRI(cyc). Trivial within-subject correlations were found between rHRI and performance, but the strength of relationship between rHRI(run) and performance was largely associated with (V) over dotO(2peak) following LT (r = -0.58 +/- 0.38). Conclusions: Performance reductions were most sensitively tracked by rHRI(run) following HT. This may be due to rHRI(run) being assessed at a higher intensity than rHRI(cyc), inferred from a higher steady-state HR and supported by a stronger within-subject relationship between rHRI(run) and performance in individuals with a lower (V) over dotO(2peak), in whom the same exercise intensity would represent a greater physiological stress. rHRI assessed at relatively high exercise intensities may better track performance changes. (C) 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.