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

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.

Prospective intervention.

rHRI was assessed during five min of cycling at 100W (rHRIcyc) and running at 8km/h (rHRIrun) 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˙O2peak).

Performance likely decreased following HT (Effect size±90% confidence interval=-0.18±0.09), then very likely increased following RP (0.32±0.14). rHRIcyc very likely decreased (-0.48±0.24), and rHRIrun 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 rHRIcyc than rHRIrun. A large correlation was found between reductions in performance and rHRIrun (r±90%; CI=0.65±0.34) from LT to HT, but was unclear for rHRIcyc. Trivial within-subject correlations were found between rHRI and performance, but the strength of relationship between rHRIrun and performance was largely associated with V˙O2peak following LT (r=-0.58±0.38).

Performance reductions were most sensitively tracked by rHRIrun following HT. This may be due to rHRIrun being assessed at a higher intensity than rHRIcyc, inferred from a higher steady-state HR and supported by a stronger within-subject relationship between rHRIrun and performance in individuals with a lower V˙O2peak, in whom the same exercise intensity would represent a greater physiological stress. rHRI assessed at relatively high exercise intensities may better track performance changes.