Adjusting For Exercise Intensity Attenuates Sex Differences In Blood Pressure During Exercise In Healthy Adults

Abstract

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 attenuated after adjustment for submaximal HG squeezing force. METHODS: We analyzed data from 95 participants including 34 females (age: 24±4 years, BMI: 24±4 kg/m2, screening BP: 106±13/64±9 mmHg, Mean ± SD) and 61 males (age: 25±5 years, BMI: 2±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 static static HG exercise at 40% of their average MVC for two minutes followed by three minutes of PEI via brachial 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 HG force as a covariate). RESULTS: Females exhibited a lower absolute 40% HG force than males (105±30 N v. 169±45 N, p<0.001). There was a significant sex x time interaction for ∆ systolic BP during HG (e.g., minute 2, females: 20±12 mmHg v. 28±18 mmHg in males, p=0.014), but not ∆ diastolic (p=0.106) or ∆ mean BP (p=0.058). After adjusting for absolute HG force, the sex difference for peak ∆ systolic BP during HG was attenuated (p=0.072). During PEI there were sex x time interactions for ∆ systolic, ∆ diastolic, and ∆ mean BP (p<0.05 for all) and adjustment for HG force did not attenuate these differences. Additionally, in a small strength-matched cohort (N=48, 29 females, female HG force mean = 107±23 N, male HG force mean = 118 ± 24 N, p=0.092) there was not a significant sex difference for peak ∆ systolic BP during HG (p=0.667) or PEI (p=0.828). CONCLUSIONS: Our data indicate that the sex difference in BP reactivity is attenuated after adjusting for absolute HG force during exercise.