Postexercise autonomic function after repeated-sprints training

PURPOSE: We examined the effects of an 8-week repeated-sprint (RS) training protocol on postexercise parasympathetic reactivation (PNSr) in healthy adults. METHODS: Eighteen male adults (24.3 ± 3.7 years) were assigned to either of two groups. One group (n = 9) performed RS training (EXP, 3 times week-1, 18 maximal all-out 15-m sprints interspersed with 17 s of passive recovery); the other served as the control group (CON, n = 9). Performance before, during, and after was assessed by measuring RS ability time (S dec) and total sprint time. The subjects were then seated for 10 min immediately after each trial and postexercise HR recovery (HRR), and vagal-related HR variability (HRV) indices were measured. RESULTS: All subjects demonstrated a decrease in S dec. However, only EXP showed a decrease in total sprint time (-10.5 % of baseline value). Using a qualitative statistical analysis method, we found a likely to almost certain positive effect of RS training on HR. The mean of each HRR and HRV index indicated a greater change in PNSr in EXP than in CON (e.g. with a 78/22/1 % chance to demonstrate a positive/trivial/negative effect on HRR60s after RS training; 74/21/5 % on LN rMSSD5-10min). Large correlations were noted between the changes in S dec [r = 0.59, 90 % CI (0.43)], total sprint time [r = -0.61 (0.42)] and HRR60s. CONCLUSION: RS training seems to be an effective method to improve postexercise PNSr in healthy adults. Also, HRR60s appears to be a method for evaluating positive adaption to RS training.