Do Oral Contraceptives Change the Ventilatory Response to Group III/IV Skeletal Muscle Afferent Activation?

BackgroundGroup III/IV skeletal muscle afferents increase ventilation (VE) during exercise. Estrogen has been show to attenuate group III/IV afferent activity. Further, oral contraceptives (OC) lower endogenous estrogen and have been shown to increase VE at rest, although the effect of OCs on VE when group III/IV afferents are activated remains unclear.ObjectiveDetermine the influence of OC use on VE in response to activation of group III/IV skeletal muscle afferents during steady state cycling in healthy, young women.MethodsFifteen women (24±2 years, mean ± SD, 8 OC‐users) completed two exercise sessions; once during the low estrogen/low hormone phase (LH, days 1–4 of the menstrual cycle for n‐OC; placebo pill for OC) and once during the high estrogen/high hormone phase (HH, days 10–14 of the menstrual cycle; active hormone pill for OC). Exercise sessions included 25 minutes of steady‐state cycling at a workload of 60W and speed of 65–70rpm. To activate group III/IV afferents, randomized sub‐systolic occlusion at three pressures (20mmHg, 60mmHg and 100 mmHg) were applied bilaterally to the proximal thigh via Hokanson cuffs (DE Hokanson, Inc., Bellevue, WA). After 3 minutes of control (CTL) exercise, cuffs were inflated for two minutes and deflated for five minutes intermittently during exercise. VE, respiratory rate (RR) and tidal volume (VT) were continuously monitored (Ultima CardiO2, MGC Diagnostics, St. Paul, MN).ResultsSub‐systolic circulatory occlusion increased VE from baseline exercise to 100 mmHg (CTL: 27.5±3.5L/min; 100 mmHg: 33.0±3.0 L/min, p<0.001). There were no differences in relative VE (%baseline exercise) following group III/IV afferent activation among OC versus n‐OC users at pressures of 20mmHg (5.9±4.9% vs. 10.2±10.3%, respectively), 60mmHg (15.4±7.5% vs. 12.2±5.4%, respectively) and 100mmHg (22.6±8.2% vs. 19.0±7.8%; respectively, p=0.08). Relative changes in RR and VT (%baseline exercise) also did not differ among OC versus n‐OC users at with increasing cuff occlusion pressures (RR: p=0.39; VT: p=0.37).ConclusionsAlthough OCs lower serum levels of sex hormones, the reduction in endogenous estrogen does not seem to influence the ventilatory response to group III/IV afferent activation in healthy, young women.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.