(604.11) Examining Vascular Responses to Passive Movement in Premenopausal Females: Comparisons Across Sex and Menstrual Cycle Phase

Poster Board Number: E478

Jennifer Weggen (Virginia Commonwealth University), Austin Hogwood (University of Virginia), Kevin Decker (University of Delaware), Ashley Darling (University of Texas Arlington), Alex Chiu (Virginia Commonwealth University), Jacob Richardson (Virginia Commonwealth University), Ryan Garten (Virginia Commonwealth University)

Purpose: Vascular responses to passive movement represent a novel assessment of vascular function and serves as a critical component for adequate blood flow regulation during exercise. Although alterations to estradiol (E2) throughout the menstrual cycle, as well as sex differences, are known to impact vascular function, limited research exists in determining whether vascular responses to passive movement are altered in premenopausal females when compared across sex or menstrual cycle phase. We hypothesized that there would be no differences in leg blood flow responses to passive leg movement (PLM) in premenopausal females when compared to age-matched males or when evaluated across follicular menstrual cycle phases, when E2 fluctuates the most.

Methods: Vascular responses to one-minute of PLM were assessed in eleven premenopausal females (n = 21; 23 ± 4 yrs) and age-matched males (n = 21; 24 ± 4 yrs). All the females completed the PLM assessment during the early (EF) and late follicular (LF) phase of their menstrual cycle, based on self-reporting of menses. Lower limb microvascular function was assessed during PLM via changes in leg blood flow measured as peak change from baseline (LBFΔPEAK) and area-under-the-curve (LBF AUC). Thigh volume, a known modulator of PLM responses, was also assessed in the passively moved limb in all participants via anthropometric measurements. Blood samples were obtained at rest from the antecubital vein of the arm to determine differences in E2 between the EF and LF phases of the menstrual cycle.

Results: Thigh volume differed significantly between the females and age-matched males (F: 4.9 ± 1.5 L; M: 8.2 ± 1.6 L; p lt; 0.01) and, when examined in all participants, thigh volume was significantly correlated to PLM-induced hyperemia evaluated as both LBFΔPEAK (r = 0.6; p lt; 0.01) and LBF AUC (r = 0.4; p = 0.014). When the group differences in thigh volume were accounted for in the PLM analysis by employing thigh volume as a co-variate, no significant differences in LBFΔPEAK (F: 542 ± 444; M: 794 ± 444 ml; p = 0.15) and LBF AUC (F: 164 ± 227; M: 249 ± 227 ml; p = 0.3) were revealed. The females reported no significant differences in PLM-induced blood flow responses across menstrual cycle phases (EF vs LF) evaluated as LBFΔPEAK (EF: 385 ± 186; LF: 386 ± 154 ml; p = 0.9) or LBF AUC (EF: 123 ± 100; LF: 58 ± 84 ml; p = 0.11). Plasma E2 levels were significantly higher in females in the LF phase (215 ± 149 pg/ml) when compared to the EF phase (149 ± 98 pg/ml) of the menstrual cycle (p = 0.01).

Conclusion: This study revealed no differences in PLM-induced LBF responses in premenopausal females when compared to age-matched males or when assessed across follicular menstrual cycle phases.