J Appl Physiol (1985). 2023 Oct 5. doi: 10.1152/japplphysiol.00775.2022. Online ahead of print.
ABSTRACT
Females generally have smaller blood pressure (BP) responses to isolated muscle mechanoreflex and metaboreflex activation compared to males, which may explain sex differences in BP responses to voluntary exercise. The mechanoreflex may be sensitized during exercise, but whether mechanoreflex-metaboreflex interactions differ by sex or variations in sex hormones remains unknown. Thirty-one young healthy subjects (females, n=16) performed unilateral passive cycling (mechanoreflex), active cycling (40% peak Watts), post-exercise circulatory occlusion (PECO; metaboreflex), and passive cycling combined with PECO (combined mechanoreflex and metaboreflex activation). Beat-to-beat BP, heart rate, inactive leg vascular conductance, and active leg muscle oxygenation were measured. Ten females underwent exploratory testing during low- and high-hormone phases of their self-reported menstrual cycle or oral contraceptive use. Systolic BP and heart rate responses did not differ between sexes during active cycling (∆30±9 vs. 29±11mmHg [males vs. females], P=0.9; ∆33±8 vs. 35±6beats/min, P=0.4) or passive cycling with PECO (∆26±11 vs. 21±10mmHg, P=0.3; ∆14±7 vs. 18±15beats/min, P=0.3). Passive cycling with PECO revealed additive, not synergistic, effects for systolic BP (males: ∆23±14 vs. 26±11mmHg, [sum of isolated passive cycling and PECO vs. combined activation]; females: ∆26±11 vs. 21±12mmHg, interaction P=0.05). Results were consistent in subset analyses with sex differences in active cycling BP (P>0.1) and exploratory analyses of hormone phase (P>0.4). Despite a lack of statistical equivalence, no differences in cardiovascular responses were found during combined mechanoreflex-metaboreflex activation between sexes or hormone levels. These results provide preliminary data regarding the involvement of muscle mechanoreflex-metaboreflex interactions in mediating sex differences in voluntary exercise BP responses.
PMID:37795529 | DOI:10.1152/japplphysiol.00775.2022
