Discrepency Between Evidence and Theory of Myoglobin S0₂ in Work

Abstract

Gayeski, Federspiel and Honig [11] showed that myoglobin Po₂ during maximum electrically stimulated exercise in dog gracilis muscle fell as low as 1 torr, but usually was limited to 3–5 torr, and was remarkably uniform, suggesting that much of the diffusion gradient for 0₂ was between red cells and myocytes. Myoglobin is 50% saturated at about 4 torr, pH = 7, and has no Bohr effect. Its dissociation curve is a single exponential. In recent experiments Richardson et al. [2], using ¹H MRS quantification of the quadriceps myoglobin.signal with one leg exercise in human volunteers, indicated that S_Mb0₂ fell with mild exercise (25% Vo_2max) to about 50%, but remained at that level at four higher work levels (approaching Vo_2max).