We compared reflex responses to static handgrip at 30% maximal voluntary contraction (MVC) in 10 women (mean age 24.1 ± 1.7 yr) during two phases of their ovarian cycle: the menstrual phase (days 1-4) and the follicular phase (days 10-12). Changes in muscle sympathetic nerve activity (MSNA; microneurography) in response to static exercise were greater during the menstrual compared with follicular phase (phase effect P = 0.01). Levels of estrogen were less during the menstrual phase (75 ± 5.5 vs. 116 ± 9.6 pg/ml, days 1-4 vs. days 10-12; P = 0.002). Generated tension did not explain differences in MSNA responses (MVC: 29.3 ± 1.3 vs. 28.2 ± 1.5 kg, days 1-4 vs. days 10-12; P = 0.13). In a group of experiments with the use of 31p- NMR spectroscopy, no phase effect was observed for H+ and H2PO4/- concentrations (n = 5). During an ischemic rhythmic handgrip paradigm (20% MVC), a phase effect was not observed for MSNA or H+ or H2PO4/- concentrations, suggesting that blood flow was necessary for the expression of the cycle-related effect. The present studies suggest that, during static handgrip exercise, MSNA is increased during the menstrual compared with the follicular phase of the ovarian cycle.
All Science Journal Classification (ASJC) codes
- Physiology (medical)