The Influence of Oxygen Saturation on the Relationship Between Hemoglobin Mass and VO₂max

Abstract

Hemoglobin mass (tHb) is a key determinant of maximal oxygen uptake (VO₂max). We examined whether oxyhemoglobin desaturation (ΔS_aO₂) at VO₂max modifies the relationship between tHb and VO₂max 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 VO₂max and ΔS_aO₂. In males and females respectively, VO₂max (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_aO₂ at VO₂max (%) ranged from 81.7–94.0 and 85.7–95.0. tHb was related to VO₂max when expressed in absolute terms and after correcting for body mass (r=0.94 and 0.86, respectively); correcting by ΔS_aO₂ did not improve these relationships (r=0.93 and 0.83). Additionally, there was a negative relationship between tHb and S_aO₂ at VO₂max (r=–0.57). In conclusion, across a range of endurance athletes at moderate altitude, the relationship between tHb and VO₂max was found to be similar to that observed at sea level. However, correcting tHb by ΔS_aO₂ did not explain additional variability in VO₂max despite significant variability in ΔS_aO₂; this raises the possibility that tHb and exercise-induced ΔS_aO₂ are not independent in endurance athletes.

Key words

endurance performance - oxygen transport - exercise-induced desaturation - hypoxia - altitude

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