Women at Altitude: Sex-Related Physiological Responses to Exercise in Hypoxia

Figures

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  Fig. 1. Schematic representation of altitude-related changes in convective (calculated from V̇O2 = cardiac output × difference in arterio-venous O2 content, sigmoid line, [236]) and diffusive (calculated from V̇O2 = diffusion coefficient × mixed venous O2 pressure, straight line, [236]) components of V̇O2max in one male and female individual matched for sea-level V̇O2max. The full line is in normoxia, the dotted line is in hypoxia (5260 m). The individual datasets are from [237]. Cardiac output was computed with pulse wave contouring analysis. The convective component was reduced to a larger extent in female individual due to a higher altitude-induced hypoxemia and lower hemoglobin concentration, while no clear differences in cardiac hemodynamic responses were noted. Due to a higher compensatory vasodilation and lower sympathetic vasoconstrictor activity, the diffusive component of V̇O2max was improved in female individuals in hypoxia. Therefore, female individuals seem more centrally but less peripherally limited than men when exercising in hypoxia. V̇O2 oxygen uptake, PO2 oxygen pressure

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  Fig. 2. Schematic representation of estrogen (blue curve) and progesterone (red curve) expected in eumenorrheic women and their potential influence on altitude-related physiological responses. The transition from follicular to luteal phase is determined by ovulation. The gray half circles represent each phase and the black line illustrates the schematic representation of the hormonal environment (related to the sum of estrogens and progesterone). HVRe hypoxic ventilatory response at exercise, SaO2 oxygen arterial saturation

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  Fig. 3. Mechanisms of sex-related differences in response to hypoxia. HVR hypoxic ventilatory response, SaO2 oxygen saturation, BP blood pressure, HR heart rate. References: Lung and airway volume [37, 38, 44], Ventilatory constraints [22, 23, 33], Exercise-induced hypoxemia [27, 28, 33], BP and HR during exercise [57–59], Microvascular responses to occlusion and exercise [122, 127], Muscle composition [130], Substrate preferences in endurance exercise [129]