The Influence of Oxygen Saturation on the Relationship Between Hemoglobin Mass and VO (2) max

Hemoglobin mass (tHb) is a key determinant of maximal oxygen uptake (VO (2) max). We examined whether oxyhemoglobin desaturation (ΔS (a) O (2) ) at VO (2) max modifies the relationship between tHb and VO (2) max at moderate altitude (1,625 m). Seventeen female and 16 male competitive, endurance-trained moderate-altitude residents performed two tHb assessments and two graded exercise tests on a cycle ergometer to determine VO (2) max and ΔS (a) O (2) . In males and females respectively, VO (2) max (ml·kg (−1) ·min (−1) ) ranged from 62.5–83.0 and 44.5–67.3; tHb (g·kg (−1) ) ranged from 12.1–17.5 and 9.1–13.0; and S (a) O (2) at VO (2) max (%) ranged from 81.7–94.0 and 85.7–95.0. tHb was related to VO (2) max when expressed in absolute terms and after correcting for body mass (r=0.94 and 0.86, respectively); correcting by ΔS (a) O (2) did not improve these relationships (r=0.93 and 0.83). Additionally, there was a negative relationship between tHb and S (a) O (2) at VO (2) max (r=–0.57). In conclusion, across a range of endurance athletes at moderate altitude, the relationship between tHb and VO (2) max was found to be similar to that observed at sea level. However, correcting tHb by ΔS (a) O (2) did not explain additional variability in VO (2) max despite significant variability in ΔS (a) O (2) ; this raises the possibility that tHb and exercise-induced ΔS (a) O (2) are not independent in endurance athletes.