Influence of exercise modality on cardiac parasympathetic and sympathetic indices during post-exercise recovery

Objectives: This study investigated indirect measures of post-exercise parasympathetic reactivation (using heart-rate-variability, HRV) and sympathetic withdrawal (using systolic-time-intervals, STI) following upper- and lower-body exercise. Design: Randomized, counter-balanced, crossover. Methods: 13 males (age 26.4 ± 4.7 years) performed maximal arm-cranking (MAX-ARM) and leg-cycling (MAX-LEG). Subsequently, participants undertook separate 8-min bouts of submaximal HR-matched exercise of each mode (ARM and LEG). HRV (including natural-logarithm of root-mean-square-of-successive-differences, Ln-RMSSD) and STI (including pre-ejection-period, PEP) were assessed throughout 10-min seated recovery. Results: Peak-HR was higher (p = 0.001) during MAX-LEG (182 ± 7 beats min−1) compared with MAX-ARM (171 ± 12 beats min−1), while HR (p < 0.001) and Ln-RMSSD (p = 0.010) recovered more rapidly following MAX-ARM. PEP recovery was similar between maximal bouts (p = 0.106). HR during submaximal exercise was 146 ± 7 (LEG) and 144 ± 8 beats min−1 (LEG) (p = 0.139). Recovery of HR and Ln-RMSSD was also similar between submaximal modalities, remaining below baseline throughout recovery (p < 0.001). PEP was similar during submaximal exercise (LEG 70 ± 6 ms; ARM 72 ± 9 ms; p = 0.471) although recovery was slower following ARM (p = 0.021), with differences apparent from 1- to 10-min recovery (p ≤ 0.036). By 10-min post-exercise, PEP recovered to baseline (132 ± 21 ms) following LEG (130 ± 21 ms; p = 0.143), but not ARM (121 ± 17 ms; p = 0.001). Conclusions: Compared with submaximal lower-body exercise, HR-matched upper-body exercise elicited a similar recovery of HR and HRV indices of parasympathetic reactivation, but delayed recovery of PEP (reflecting sympathetic withdrawal). Exercise modality appears to influence post-exercise parasympathetic reactivation and sympathetic withdrawal in an intensity-dependent manner. These results highlight the need for test standardization and may be relevant to multi-discipline athletes and in clinical applications with varying modes of exercise testing.