Sympathoexcitation via post-exercise circulatory occlusion altered heart rate tau compared to control (28 vs 23 s; P=0.362, Cohen's d=1.1) during moderate-intensity exercise.
Does sympathoexcitation via isometric handgrip and post-exercise circulatory occlusion alter heart rate kinetics during moderate-intensity exercise in healthy volunteers?
Sympathoexcitation induced by handgrip and circulatory occlusion may modulate heart rate kinetics and amplitude at the onset of moderate-intensity exercise, though findings in this small sample were not statistically significant.
Effect estimate: Cohen's d 1.1
Absolute Event Rate: 28% vs 23%
p-value: p=0.362
Background: At exercise onset sympathovagal balance shifts toward sympathetic dominance with the initial rapid heart rate increase modulated primarily by a reduction in vagal activity. It remains unclear whether greater sympathetic activity at the onset of exercise alters the kinetics of heart rate. We tested the hypothesis that sympathoexcitation during the exercise transient would slow heart rate kinetics during moderate-intensity exercise. Methods: Four healthy volunteers (1F/3M; mean(SD), 21(2) yrs; 177.5(4.1) cm; 76.9(3.0) kg; 24.4(1.6 ) kg/m 2 ) performed cycle ergometry within the moderate intensity exercise domain (105 W). Control (CTL) trials consisted of rest to exercise at for 5 min. Sympathoexcitation trials comprised of 2-min bilateral isometric handgrip at 40% maximal voluntary contraction, followed by 2 min of post-exercise circulatory occlusion (PECO) performed at rest and during the first 4 min of exercise. PECO was then terminated and exercise continued for an additional 1 min. Each condition was repeated in triplicate. Beat-by-beat heart rate (ECG) from each trial within a condition for each subject was interpolated to 1-s time bins, time-aligned, and averaged to yield a single response profile, then binned into 5-s averages. Heart rate kinetics were determined using a mono-exponential model. Data were compared using two-tailed paired t-tests and Cohen’s d effect size analysis. Results: There was a large effect of PECO (82(7) beats/min) on the pre-exercise heart rate compared to CTL (76(6) beats/min, P = 0.1688, Cohen’s d = 0.9). There was a medium effect of PECO (37(11) beats/min) on heart rate amplitude compared to CTL (43(3) beats/min, P = 0.189, Cohen’s d = 0.7). There was a large effect of PECO (28(5) s) on heart rate tau compared to CTL (23(4) s, P = 0.362, Cohen’s d = 1.1). To further examine the amplitude modulation of sympathoexcitation on heart rate, the heart rate change from PECO to cuff deflation during exercise was determined. Heart rate decreased (large effect) from 119(4) beats/min to 114(5) beats/min from PECO to cuff deflation (P = 0.080, Cohen’s d = 1.1). The 5(4) beats/min reduction in heart rate with PECO cessation during exercise contrasts a 0(1) beats/min change in heart rate (large effect) over the same timepoint during CTL (P = 0.072, Cohen’s d = 1.7). Conclusion: Sympathoexcitation during the exercise transient may modulate the kinetics and amplitude of heart rate within the moderate intensity exercise domain. Funding: Heart and Stroke Foundation of Canada. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Lundquist et al. (Fri,) conducted a other in Healthy volunteers (n=4). Sympathoexcitation (isometric handgrip and post-exercise circulatory occlusion) vs. Control (rest to exercise) was evaluated on Heart rate tau (kinetics) (Cohen's d 1.1, p=0.362). Sympathoexcitation via post-exercise circulatory occlusion altered heart rate tau compared to control (28 vs 23 s; P=0.362, Cohen's d=1.1) during moderate-intensity exercise.