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UBC Theses and Dissertations

Limb and inspiratory metaboreflex activation in healthy males and females Benbaruj, Jenna


The muscle metaboreflex is a cardiovascular control mechanism that contributes to the reflex increase in mean arterial pressure (MAP) and blood flow redistribution during exercise, to meet metabolic demands. The MAP response to metaboreflex activation is attenuated in females compared to males, during both limb and respiratory muscle work. Whether this sex-based difference is similar in magnitude across muscle groups is currently not well-understood. PURPOSE: The purpose of this thesis was to compare sex-based differences in the pressure response to limb and inspiratory metaboreflex activation, during relative and absolute workloads. METHODS: Seventeen healthy participants (n=9 males, n=8 females) completed two experimental visits; the first visit included pulmonary function tests, forearm volume and circumference measurements, and two bouts of exercise. The second day mimicked the first, except with no pulmonary function measurements. The exercise performed on both days were acute bouts of intermittent handgrip exercise (IHE) and pressure threshold loading (PTL) to volitional exhaustion, performed in a randomized order, and separated by 30-min of rest. PTL is a resistive breathing task that requires participants to generate large inspiratory pressures to overcome a threshold load, and attain unimpeded breathing. Participants exercised at a predetermined relative (R) or absolute (A) workload, and cardiopulmonary measurements were recorded continuously throughout. RESULTS: 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-IHE: ∆31±12 mmHg; R-PTL: ∆31±9; A-IHE: ∆35±6; A-PTL: ∆30±7) than females (R-IHE: ∆21±7 mmHg; R-PTL: ∆13±7; A-IHE: ∆21±7; A-PTL: ∆14±3) (p<0.001). CONCLUSION: The present study observed a time-dependent increase in MAP in both males and females, in response to comparable amounts of limb and respiratory muscle work. The MAP response was greater in males than females, regardless of muscle group or workload. 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.

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