On and off responses of heart rate to supramaximal exercise in non-athletes

Abstract

BACKGROUND: The on-response of heart rate (HR) to exercise at high intensities results from both parasympathetic inhibition and sympathetic activation, while the off-response is characterized by parasympathetic reactivation but not much is known about the actual start of HR recovery (HRR). METHODS: Twenty-eight sedentary male non-athletes performed a 30-s Wingate Anaerobic Test on a cycle ergometer and the increase in HR during exercise (on-response; HRon) and decrease in the recovery (off-response) were modeled with attention to the delay of the onset of HRR. RESULTS: The HRonshowed moderate correlation with cHRonotropic slope (CS, increase of HR to age predicted HR maximum) (r=0.593, P<0.05). Strong correlation was found between HR off-parameters: HRR60(difference between the inal HR at exercise completion and the HR recorded following 60 secs) and Toff (time constant describing the shape of the HR off-response) (r=0.7, P<0.05) and moderate between HRR60and T30(r=0.6, P<0.05) and Toff and T30(negative reciprocal of the slope of the regression line of HR for the irst 30 secs of HRR) (r=0.611,P<0.05). HR returned to a stable values after 5 min of recovery but was higher than at rest (P<0.05). The delay between the protocol start of recovery and start (t0) was 5.2±1.0 s and correlated with time constant describing the shape of the HR onresponse (Ton) (0.723, P<0.05), and moderately with HRon(0.455, P<0.05) and CS (0.513, P<0.05). CONCLUSIONS: We found no correlation between on- and off-responses of HR during supramaximal exercise. We also found that there is a 5.2±0.1 sec delay to when HR starts to decrease following intense exercise cessation and it correlates with the parameters of cardioacceleration Ton, HRon(time constant describing the shape of the HR onresponse) and CS.