Modeling O₂ transport as an integrated system limiting (.)V(O₂MAX).
Maximal endurance exercise capacity is determined by a variety of factors, including maximal ability to transport O₂ to the muscle mitochondria and to use this O₂ for ATP generation ((.)V(O₂MAX)). This analysis combines the individually well-known O₂ mass conservation equations for the four critical steps in the O₂ transport pathway (ventilation, alveolar/capillary diffusion, circulation and muscle diffusion) into an analytical, closed form, model showing how (.)V(O₂MAX) depends on all four steps. It further shows how changes in any one step affect the function of the others. This analytical approach however requires approximating the O₂Hb dissociation curve as linear. Removing this condition to allow for the real O₂Hb curve requires numerical analysis best explained graphically. Incorporating maximal mitochondrial metabolic capacity to use O₂ allows prediction of when (.)V(O₂MAX) is limited by transport or by metabolic capacity. This simple approach recapitulates in vivo behavior and clarifies the determinants of maximal exercise.
Wagner
Peter D
PD
Division of Physiology, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, DEPT 0623A, La Jolla, CA 92093-0623A, USA. pdwagner@ucsd.edu
D006801:Humans; D010100:Oxygen / Q000378:metabolism*; D010807:Physical Endurance; D012129:Respiratory Function Tests
D010100:Oxygen