Inter-individual variation in SpO2 during endurance exercise in hypoxia does not correlate with endocrine and angiogenic growth factor responses.

The present study determined the relationship between inter-individual variation in arterial O₂ saturation (SpO₂) and exercise-induced endocrine and angiogenic growth factor responses under hypoxia. Sixteen healthy men completed two trials on separate days: 60 min of cycling at 65% of maximal oxygen uptake (VO₂max) followed by a 60-min rest period, under either normoxia (FiO₂ = 20.9%, NOR) or hypoxia (FiO₂ = 14.5%, HYP). Serum growth hormone (GH), cortisol, and vascular endothelial growth factor (VEGF) concentrations were determined before, immediately after, and at 60 min after exercise. SpO₂ and heart rate were continuously measured during exercise. In the HYP trial, the average SpO₂ during exercise varied by >10% among all participants (77.5%-88.2%). However, the ΔSpO₂ (Δ = HYP-NOR) did not correlate significantly with exercise-induced changes in serum ΔGH (r = 0.205, p = 0.446), Δcortisol (r = 0.059, p = 0.828), and ΔVEGF (r = -0.004, p = 0.989). Moreover, no significant correlations were observed between the absolute SpO₂ value and exercise-induced responses in these blood variables in the HYP trial. Inter-individual variation in SpO₂ did not modify exercise-induced endocrine (GH, cortisol) or angiogenic growth factor (VEGF) responses to endurance exercise in hypoxia.