Effect of Endurance Training on the Autonomic Nervous System Function of Young Male

In this study, healthy young males were randomized into groups with moderate intensity training (n = 24), high intensity training (n = 24) and utmost intensity training (n = 24). At the end of 8-week training period, HRV measurements demonstrated a marked increase of RMSSD (P = 0.003), PNN50 (P = 0.002), HF (P = 0.002), SDNN (P = 0.002) and LF (P = 0.003) in the moderate intensity group and a decreasing tendency in LFn and LF/HF; however, in the utmost intensity group HFn (P = 0.012) decreased prominently while its LF (P = 0.032), LFn (P = 0.039) and LF/HF (P = 0.015) increased significantly. Nevertheless marked changes were not found in the above indexes of the high intensity group. While resting HR of the three groups declined significantly at the end of 8 weeks (P was 0.001, 0.0001 and 0.001 respectively); RMSSD, PNN50, HF, LF and SDNN were significantly higher in the moderate intensity group than in the other two groups (P < 0.05 or 0.01). Compared with the moderate intensity group, HFn of the utmost-intensity group (P = 0.012) was significantly lower but its LFn and LF/HF were markedly higher (P was 0.025 and 0.015 respectively); LF/HF of both the high and utmost intensity group was significantly higher (P was 0.033 and 0.037 respectively). Despite a significant reduction of plasma NE in all the three groups at the end of 8-week training period (P was 0.016, 0, 0.031 respectively), plasma NE level of moderate and high intensity group was much lower than that of the utmost intensity group (P was 0.001, 0 respectively). Utmost and moderate endurance training results in altered sympathetic and parasympathetic balance towards sympathetic dominance and parasympathetic dominance respectively; whereas high intensity endurance training almost has no effect on ANS function. CPT and HUTT reveal the potential danger posed by utmost intensity endurance training.