Influence of Exercise Mode on Post-Exercise Indices Reflecting Cardiac Parasympathetic Reactivation and Sympathetic Withdrawal: 2564 Board #84 June 2 9

PURPOSE: 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 dynamic exercise. METHODS: 13 males (age 26.4±4.7 y) performed maximal incremental arm-crank and leg cycling exercise tests (MAX-ARM and MAX-LEG, respectively). Subsequently, participants performed separate 8-min bouts of submaximal HR-matched exercise of each mode (SUBMAX-ARM and SUBMAX-LEG). HRV (including the natural-logarithm of root mean square of successive differences, Ln-RMSSD) and STI (including the pre ejection period, PEP) were assessed throughout 10-min seated recovery. RESULTS: Peak HR was higher (p=0.001) during MAX-LEG (182±7 b.min-1) compared with MAX-ARM (171±12 b.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 exercise bouts (p=0.106). HR during submaximal exercise was 146±7 and 144±8 b.min-1 for SUBMAX-LEG and SUBMAX-ARM, respectively (p=0.139). The recovery of HR and Ln-RMSSD was also similar between submaximal modes (p=0.219 and 0.110, respectively), although these variables did not return to resting levels (p<0.001). PEP was similar at end-exercise (SUBMAX-LEG 70±6 ms; SUBMAX-ARM 72±9 ms; p=0.471), however PEP recovery was slower following SUBMAX-ARM (p=0.021), with differences between modes apparent over 1 to 10-min recovery (p≤0.036). By 10-min post-exercise, PEP had recovered to near-resting levels (132±21 ms) following SUBMAX-LEG (130±21 ms; p=0.143) but not after SUBMAX-ARM (121±17 ms; p=0.001). CONCLUSION: Compared with submaximal HR-matched lower-body exercise, upper-body dynamic exercise elicited a similar recovery of HR and HRV indices of parasympathetic reactivation, but a delayed recovery of PEP (index of sympathetic withdrawal). These data indicate that exercise mode influences post-exercise parasympathetic reactivation and sympathetic withdrawal in a manner that is moderated by exercise intensity. These results may be of practical relevance to multi-discipline athletes, as well as for clinical monitoring applications where the mode of exercise testing may vary.