Exponential modelling of heart rate recovery after a maximal exercise

Objectives: Heart rate recovery (HRR) after exercise is clinically important as a predictor of mortality. In addition, HRR an indicator cardiac autonomic activity, since increased vagal activity and diminished sympathetic return the heart to resting conditions exercise. The previous attempts model using polynomial, first-order second-order modelling have produced mixed results. this study, we hypothesised that double-exponential fit would more accurately than single-exponential it capture both arms responsible for decay investigated outcome these two models on data following maximal Materials Methods: Exponential curve fitting was done set previously published from our laboratory. were acquired 40 male participants (19–38 years) treadmill normalised 5-min time window fitted single curves, obtain, respectively, constants Tau and, 1 2. goodness-of-fit assessed with Chi-square values computed each participant models. Considering zero perfect fit, therefore, smaller indicate better larger values, difference in (Δχ 2 ) between by subtracting value fit. This based premise if calculated Δχ positive, model. are presented mean ± standard deviation. Comparisons made Student’s t -test. Results: Data four excluded technical reasons. 65.50 12.13 s, while 43.75 18.96 s 120.30 91.32 being significantly lower ( P < 0.0001). Remarkably among 36 participants, positive (127.2 171.04) 22 subjects or marginally negative (−0.17 0.31) 14 subjects. Conclusion: Our results almost two-thirds (61%) study population. remaining nearly equivalent fits no evidence superior show sufficient subjects, less efficient most participants. comparison, effectively modelled 100% Given findings, conclude inclusive represented population