Exercise-induced muscle chemoreflex modulation of spontaneous baroreflex sensitivity in man.

1. The goal of this study was to determine the effect of exercise-induced muscle chemoreflex activation on baroreflex sensitivity (BRS). This is a retrospective study using data obtained during two prior studies. 2. Twenty-three subjects with a mean (S.E.M.) age of 28 (1.5) years took part in the study. Sequence analysis was performed on the systolic blood pressure (SBP) responses, measured by a Finapres, and R-R intervals, measured from the ECG. 3. Electrically evoked isometric exercise (Stim) of the triceps surae was performed for 2 min at 30 % maximum voluntary contraction force. During exercise and for a further 2 min thereafter, circulation to the lower leg was occluded by inflation of a thigh cuff to above 200 mmHg. 4. Prior to exercise mean (+/- S.E.M.) BRS was 10.92 +/- 6.3 ms mmHg(-1), and BRS remained at this level during evoked exercise (10.90 +/- 7.1 ms mmHg(-1)). BRS increased to 12.34 +/- 6.0 ms mmHg(-1) during post-exercise circulatory occlusion (PECO) (P <0.05, MANOVA, post hoc Student's paired t test vs. Stim) and fell to 9.27 +/- 4.4 ms mmHg(-1) during recovery (P <0.01 vs. PECO value, P = 0.059 vs. resting value). 5. These data indicate that during PECO following electrically evoked plantar flexion, where only muscle chemosensitive afferents were likely to be stimulated, BRS was increased.