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McKenna A. Tharpe1, Joseph C. Watso2,3, Matthew C. Babcock4,3, Michael Brian5,3, Braxton A. Linder1, Kamila U. Pollin6,3, Zach J. Hutchison1, Alex M. Barnett1, William Farquhar, FACSM3, Austin T. Robinson1,3. 1Auburn University, Auburn, AL. 2University of Texas Southwest Medical Center, Dallas, TX. 3University of Delaware, Newark, DE. 4University of Colorado Denver, Aurora, CO. 5University of New Hampshire, Durham, NH. 6Veteran Affairs Medical Center, Washington, DC.

PURPOSE: The exercise pressor reflex, composed of the muscle mechano- and metaboreflex, increases blood pressure (BP). Compared to males, healthy female adults typically exhibit blunted BP responses to exercise. However, recent work suggests that sex differences in BP during isometric handgrip (HG) exercise and post-exercise ischemia (PEI; metaboreflex isolation) are attenuated after adjusting for differences in maximal voluntary contraction (MVC). Therefore, the purpose of this study was to determine whether sex differences in BP responses during HG and PEI would be abolished after adjustment for submaximal HG squeezing force. METHODS: We analyzed data from 89 participants including 30 females (age: 24±4 years, BMI: 24±4 kg/m2, screening BP: 106±13/63±9 mmHg, Mean±SD) and 59 males (age: 24±4 years, BMI: 25±3 kg/m2, screening BP: 113±11/66±9 mmHg). All females were tested during days 1-5 of their menstrual cycle. Maximal HG force for each participant was defined as the average of three MVCs. Following a 10-minute baseline period, participants performed isometric static HG exercise at 40% of their average MVC for two minutes followed by three minutes of PEI via brachial artery occlusion. We obtained beat-to-beat BP readings via finger photoplethysmography (Finometer). Statistical analyses included t-tests, 2-way ANOVAs (sex x time) and ANCOVAs (average force during HG minute 2 as a covariate). RESULTS: Females exhibited a lower absolute 40% HG force than males (106±30 N v. 163±48 N, p=0.026). There was a significant sex x time interaction for peak (minute 2) ∆ systolic BP during HG (females: 19±12 mmHg v. 27±17 mmHg in males, p=0.022), but not diastolic (p=0.126) or mean BP (p=0.076). After adjusting for absolute HG force, the sex difference for ∆ systolic BP during HG was attenuated (p=0.095). Additionally, in a small strength-matched cohort (N=48, 28 females, female HG force mean = 106±26 N, male HG force mean = 120±25 N, p=0.078) there was not a significant sex difference for peak ∆ systolic BP during HG (p=0.200). During PEI there were sex x time interactions for systolic, diastolic, and mean BP (p<0.01 for all) and adjustment for HG force did not attenuate these differences. CONCLUSION: Our data indicate that the sex difference in BP reactivity is attenuated after adjusting for absolute HG force during exercise, but not metaboreflex isolation.

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