Author(s): CALLOVINI, A., FORNASIERO, A., SAVOLDELLI, A., BORTOLAN, L., PELLEGRINI, B., CAPELLI, C., SCHENA, F., Institution: CERISM - UNIVERSITY OF VERONA, Country: ITALY, Abstract-ID: 2263

INTRODUCTION:
Sex differences in exercise physiology are underrepresented in the literature, particularly in specific contexts such as High Altitude (HA)1. The aim of this study was to investigate the influence of sex on the cardiac and respiratory responses to exercise at sea level (SL) and HA.
METHODS:
Eight women (F; VO2max:49±3 mL/kg/min) and eight height-matched men (M; VO2max:59±5 mL/kg/min) underwent a VO2max test, at SL (20.9 FiO2) and at a simulated altitude of 4500m (11.8 FiO2). These were followed by two pulmonary function (PF) evaluation sessions, one at SL and one at HA, where cardio-respiratory responses, Inspiratory Capacity (IC), and Diffusion Capacity (DLCO) were assessed during moderate (mod), heavy (heav) and severe (sev) exercise.
RESULTS:
VO2max (F:-32%, M:-31%), VEmax (F:-8%, M:-7% ) and HRmax (F:-6%, M:-6%) were significantly reduced at HA (all p<0.001). During PF, submaximal VO2 was lower at HA (p<0.001) in both sexes, with a sex*intensity interaction effect (p<0.001) indicating progressively higher sex differences with increasing exercise intensity regardless of condition. SpO2 was significantly reduced at HA (≈ -29%), with no general effect of ‘sex’ or ‘intensity’. Submaximal ventilation (VE) was similar between sexes at SL, whereas it was significantly lower during heav and sev at HA in women if compared to men (condition*intensity*sex interaction, p=0.021). Cardiac responses (i.e., Q, SV, and HR) showed a ‘FiO2*intensity’ interaction (p=0.028, 0.004, and 0.001, respectively), displaying a trend toward a decrease at HA as exercise intensity increased (Q: ≈+6, -6, -10%; SV: ≈+4, -5, -6%; HR:≈+2, -0.4, -4% for mod, heav and sev, respectively). No sex differences were detected in these variables. Breathing responses derived from IC were reduced in females, with no additional effect of HA. DLCO values, even when corrected for Alveolar volume (Va), were lower in females at both SL and HA (p=0.023) for all the intensity domains. Finally, a reduction in DLCO (mod:-11 and -1%; heav:-12 and -6%; sev:-7 and -12% for M and F, respectively) and DLCO/Q ratio (mod:-16 and -8%; heav: -8 and -3 %, sev: -4 and -3% for M and F, respectively) was noted in both sexes at HA (p<0.001).
CONCLUSION:
Similar maximal and submaximal oxygen consumption differences between F and M have been found at SL and HA. SpO2 was reduced by hypoxia, but similar between sexes in the two conditions. Cardiac responses (e.g, HR, SV and CO) were unaffected by sex at both maximal and submaximal levels, while respiratory responses (IC and DLCO outcomes) have been confirmed to be impaired in women2, with no additional effect of HA on the sex gap already present at SL in these variables. VE differences between sexes found at HA but not SL underline the central role of ventilatory responses in determining sex differences to exercise at HA.

1. Sims ST, et al. Exp Physiol. 2018; doi:10.1113/EP086797
2. Raberin A, et al., Sport Med. 2023. doi:10.1007/s40279-023-01954-6