Cardiac Autonomic Recovery after an Acute Bout of Endurance Exercise in Adolescent and Adult Amateur Long-distance Runners

Objective:To examine the time course of heart rate variability(HRV) after an acute bout of endurance exercise in adolescent and adult male amateur runners,and elucidate the physiological significance of HRV changes post-exercise.Method:Ten adolescent(aged 14.4±1.3 years) and 10 adult(aged 25.7±2.8 years) runners performed a 90min constant-load treadmill run at 95% of individual ventilatory threshold.The HRV indexes were assessed at pre-exercise,15 min and 6 h post-exercise.Results:At 15 min post-exercise,TPLn,HFnu and HRV time domain indexes were lower than those of pre-exercise,while LFnu and LF/HF were significant increased.LFnu and LF/HF were significant lower in children than adults(P<0.05).All HRV indexes were recovered to pre-exercise level at 6 h post-exercise.Meanwhile,TPLn,SDNN,HFnu and RMSSD seemed to rebound and exceed the pre-exercise level.A significant relationship was found between changes in HFnu from baseline and age of subjects(r =-0.645,P<0.01,n=20).Additionally,the magnitudes of HFnu and TPLn suppressions post-exercise were negative associated with their baseline levels(P<0.05,n=20),respectively.Conclusion:HRV was transient suppressed after an acute bout of endurance exercise.The magnitude of HRV suppression in adolescent subjects was lower than adults following exercise.The behavior of HRV response to exercise exhibiting differently might be associated with maturity status and it might reflect the physiological adaptation to acute exercise.