Spontaneous cardiac baroreflex sensitivity is enhanced during post-exercise ischemia in men but not in women.

PURPOSE

To investigate the effect of isolated muscle metaboreflex activation on spontaneous cardiac baroreflex sensitivity (cBRS), and to characterize the potential sex-related differences in this interaction in young healthy subjects.

METHODS

40 volunteers (20 men and 20 women, age: 22 ± 0.4 year) were recruited. After 5-min rest period, the subjects performed 90 s of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 3 min of post-exercise ischemia (PEI). Beat-to-beat heart rate and arterial blood pressure were continuously measured by finger photopletysmography. Spontaneous cBRS was assessed using the sequence technique and heart rate variability was measured in time (RMSSD-standard deviation of the RR intervals) and frequency domains (LF-low and HF-high frequency power).

RESULTS

Resting cBRS was similar between men and women. During PEI, cBRS was increased in men (Δ3.0 ± 1.1 ms mmHg, P = 0.03) but was unchanged in women (Δ-0.04 ± 1.0 ms mmHg, P = 0.97). In addition, RMSSD and HF power of heart rate variability increased in women (Δ7.4 ± 2.6 ms, P = 0.02; Δ373.4 ± 197.3 ms; P = 0.04, respectively) and further increased in men (Δ26.4 ± 7.1 ms, P < 0.01; Δ1874.9 ± 756.2 ms; P = 0.02, respectively). Arterial blood pressure increased from rest during handgrip exercise and remained elevated during PEI in both groups, however, these responses were attenuated in women.

CONCLUSIONS

These findings allow us to suggest a sex-related difference in spontaneous cBRS elicited by isolated muscle metaboreflex activation in healthy humans.