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.