The Effect of Subsystolic Regional Circulatory Occlusion on Blood Pressure and Systemic Vascular Resistance in Men and Women during Exercise

Abstract

IntroductionThe exercise pressor reflex contributes to cardiovascular regulation during exercise. The primary components of the exercise pressor reflex response are the mechanically and metabolically sensitive skeletal muscle afferents (group III and IV, respectively). Experimentally, subsystolic regional circulatory occlusion (SubRCO) leads to venous distention, stimulating primarily group III afferents, thereby augmenting the exercise pressor reflex. Previous studies have reported sex differences in the metaboreflex induced exercise pressor reflex induced cardiovascular responses. Specifically, pre‐menopausal women, compared to age‐matched men, were found to have attenuated cardiovascular responses with mechanoreflex stimulation. However, it is unclear if sex differences are also present in the cardiovascular responses during exercise with locomotor limb venous distention. Therefore, the purpose of this study was to determine the influence of SubRCO during submaximal exercise in men and women. We hypothesized that women will have attenuated increases in mean arterial pressure (MAP) and systemic vascular resistance (SVR) than men during exercise with SubRCO.MethodsTwelve men and thirteen women completed two study visits (Age: M: 30±6vs. W: 27±8yrs, p>0.05; BMI: M: 25.4±3.6 vs. W: 22±3 kg/m2, p<0.05). The first visit consisted of a peak exercise ergometry test. The second visit consisted of constant‐load cycle ergometry at 30% peak workload with different SubRCO pressures via bilateral upper thigh pressure cuffs. The cuffs remained uninflated (0 mmHg) (CTL) during the first three min of exercise, then were intermittently inflated to 20, 40, 60, 80, or 100 mmHg for two minutes (randomized order). Each inflation period was followed by a 2minute deflation period where the participant continued to exercise. Cardiacoutput (Q) and MAP were measured via continuous hemodynamic photoplethysmography and systemic vascular resistance (SVR) was calculated. Data were reported as delta changes from CTL.ResultsCompared to 0 mmHg, MAP increased with SubRCO inflation pressures of 60, 80, and 100mmHg in men and women during submaximal exercise (all, p<0.05); however, no differences were present between groups (60 mmHg: M: 6.2±4.2 vs. W: 8.0±5.2; 80mmHg: M: 11.6±5.5 vs. W: 15.1±4.8; 100 mmHg: M: 18.2±6.6 vs. W: 20.5±7.2 mmHg(all, p>0.05)). Similarly, SVR increased with cuff inflation pressures of60, 80, and 100 mmHg compared to 0 mmHg in men and women (p<0.05), while no differences existed between groups (60 mmHg: M: 0.3±0.4 vs W: 0.4±0.5;80 mmHg: M: 0.9±0.5 vs W: 1.1± 0.9; 100 mmHg M: 1.3±0.8vs W: 1.5±0.8mmHg/L/min (all, p>0.05)). In contrast, Q did not change with cuff inflation pressures of 20, 40, 60, 80, or100 mmHg compared to 0 mmHg in men or women during submaximal exercise(p>0.05).ConclusionIn contrast to our hypothesis, the MAP and SVR responses were not different between men and women with SubRCO during submaximal exercise. Our findings suggest that sex differences are not present in the cardiovascular response to low‐intensity constant‐load exercise with stimulation of the exercise pressor reflex via lower limb venous distention.