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Abstract

Background: Dyspnoea is the multidimensional sensation of breathing discomfort which varies in sensory experience and affective response. During exercise, healthy adults typically report sensations of “air hunger” (AH) and “work/effort” (W/E), with females more frequently reporting AH at maximal exertion. However, interpreting this sex difference is challenging due to the complex physiological responses associated with exercise. Laboratory models can better isolate perceptual responses by inducing dyspnoea in the absence of whole-body exercise. This study aimed to characterize sex differences in the perception of laboratory induced dyspnoea and identify potential underlying neuromechanical mechanisms. Methods: 34 participants (17M:17F) completed two breathing challenges to independently target work/effort and air hunger. W/E was targeted through maximal incremental inspiratory pressure threshold loading (IPTL) with increments of 5% of the participant’s maximal inspiratory pressure (MIP). AH was targeted by constraining ventilation while increasing PETCO₂ in increments of 10% of resting values to induce hypercapnia. Mixed effects models were used to assess sex differences in the perceptual and physiological response to each stimulus. Results: IPTL: There were significant interactions between sex and stimulus for dyspnoea intensity (P=0.03) and W/E (P=0.04), with a steeper slope in males. There was no interaction between sex and stimulus for dyspnoea unpleasantness and AH (both P>0.05). There was no difference in activation of the diaphragm between sex. Females had a steeper slope in the activation of their extradiaphragmatic inspiratory muscles compared to males (P0.05). There was no difference in activation of the diaphragm between sex (P>0.05). Females had greater activation of the sternocleidomastoid inspiratory muscles compared to males at 0% and 10% ΔPETCO₂ (P