Can a first‐order exponential decay model fit heart rate recovery after resistance exercise?

Summary The time‐constant of postexercise heart rate recovery ( HRR τ ) obtained by fitting heart rate decay curve by a first‐order exponential fitting has being used to assess cardiac autonomic recovery after endurance exercise. The feasibility of this model was not tested after resistance exercise ( RE ). The aim of this study was to test the goodness of fit of the first‐order exponential decay model to fit heart rate recovery ( HRR ) after RE . Ten healthy subjects participated in the study. The experimental sessions occurred in two separated days and consisted of performance of 1 set of 10 repetitions at 50% or 80% of the load achieved on the one‐repetition maximum test [low‐intensity ( LI ) and high‐intensity ( HI ) sessions, respectively]. Heart rate ( HR ) was continuously registered before and during exercise and also for 10 min of recovery. A monoexponential equation was used to fit the HRR curve during the postexercise period using different time windows (i.e. 30, 60, 90, … 600 s). For each time window, (i) HRR τ was calculated and (ii) variation of HR explained by the model ( R 2 goodness of fit index) was assessed. The HRR τ showed stabilization from 360 and 420 s on LI and HI , respectively. Acceptable R 2 values were observed from the 360 s on LI ( R 2  > 0·65) and at all tested time windows on HI ( R 2  > 0·75). In conclusion, this study showed that using a minimum length of monitoring (~420 s) HRR after RE can be adequately modelled by a first‐order exponential fitting.