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• Under normoxia, males have a cardiac output (CO) of 6.43 ± 0.76 L.min−1 and females have 6.99 ± 0.96 L.min−1; under iso-saturation hypoxia, males have 6.85 ± 0.91 L.min−1 and females have 7.46 ± 1.16 L.min−1.
• Under normoxia, males have a cardiac index (CI) of 3.45 ± 0.33 L.min−1.m2 and females have 4.26 ± 0.42 L.min−1.m2; under iso-saturation hypoxia, males have 3.64 ± 0.34 L.min−1.m2 and females have 4.54 ± 0.55 L.min−1.m2.
• The estimated energy cost of circulation (HR) exceeded the energy cost of respiration (VE) in both normoxia and hypoxia conditions.
• There was no significant main effect for sex on oxygen saturation (SpO2) in either normoxia or hypoxia conditions.
• Under normoxia, males have a heart rate (HR) of 74 ± 10 bpm and females have 83 ± 6 bpm; under iso-saturation hypoxia, males have 77 ± 8 bpm and females have 90 ± 7 bpm.
• In a study of 22 healthy individuals (12 females), participants were exposed to 10 minutes of normoxia (FiO2 = 0.21) followed by 10 minutes of hypoxia (FiO2 = 0.115).
• The study on sex differences in cardiorespiratory control under hypoxia used an oxygen dilution system (Everest Summit II—Hypoxico®, NY, USA) coupled with two 200-L non-diffusing gas reservoirs to control the fraction of inspired oxygen (FiO2) for normoxic and hypoxic conditions.
• The researchers calculated physiological changes induced by hypoxia using the delta formula (Δ = hypoxia—normoxia) for both male and female groups.
• Under normoxia, males have a pulse oxygen saturation (SpO2) of 98 ± 1% and females have 98 ± 1%; under iso-saturation hypoxia, males have 91 ± 3% and females have 92 ± 2%.
• In the study, no sex differences in SpO2 changes were found during walking in either normoxia or hypoxia, despite significant reductions in SpO2 observed in both groups.
• Heart rate variability (HRV) analysis involves analyzing beat-to-beat time series of R-R intervals using a 300-beat time window, focusing on the last 5 minutes for normoxia and iso-time hypoxia conditions.
• Resting blood lactate concentration is similar across sexes in both normoxia (1.2 ± 0.2 mmol L−1 in men vs. 1.2 ± 0.2 mmol L−1 in women) and hypoxia (1.2 ± 0.2 mmol L−1 in men vs. 1.2 ± 0.3 mmol L−1 in women).
• Under normoxia, males have a tidal volume (Vt) of 999 ± 180 ml and females have 747 ± 125 ml; under iso-saturation hypoxia, males have 1,120 ± 206 ml and females have 753 ± 116 ml.