Sex-based differences in the blood pressure responses to muscle metaboreflex activation are consistent between limb and respiratory muscle

The purpose of this study was to compare sex-based differences in the mean arterial blood pressure (MAP) response to limb and inspiratory metaboreflex activation, during relative and absolute workloads. Healthy males (M; n=9) and females (F; n=8) completed pulmonary function testing, forearm volume and circumference measurements, and bouts of limb and inspiratory muscle exercise. The exercises performed included bouts of rhythmic handgrip exercise (RHG) and inspiratory pressure threshold loading (PTL) to task failure, performed in a randomized order, and separated by 30 minutes of rest. Participants performed both RHG and PTL at predetermined relative (R) and absolute (A) workloads while cardiopulmonary measurements were recorded continuously. A time-dependent rise in MAP was observed in all participants, regardless of sex, muscle, or workload (p<0.001). MAP was greater in males than females during all exercise bouts regardless of muscle group or workload (p<0.001). The change in MAP from baseline was also greater in males (R-RHG: ∆31±12 mmHg; R-PTL: ∆31±9; A-46 RHG: ∆35±6; A-PTL: ∆30±7) than females (R-RHG: ∆21±7 mmHg; R-PTL: ∆13±7; A-RHG: ∆21±7; A-PTL: ∆14±3) (p<0.001). Results from this study show that when the forearm and diaphragm perform the same relative or absolute work, the blood pressure response is statistically similar, and both responses are greater in males than females. The findings from the present study suggest that the sex-based difference in the response to metaboreflex activation is similar between the limb and respiratory musculature.