Muscle blood flow and distribution determine maximal VO2 of contracting muscle.

Medicine & Science in Sports & Exercise:
BASIC SCIENCES/REGULATORY PHYSIOLOGY: Symposium: Mechanisms Which Control [latin capital V with dot above]O2 Near [latin capital V with dot above]O2max: PDF Only

During repetitive contractions, the VO2 of the dog gastrocnemius-plantaris muscle rose with the contraction frequency up to a maximal value and then decreased as contraction frequency was increased further. PVO2 was constant over most of the contraction frequency range. Reducing perfusion pressure/blood flow reduced [latin capital V with dot above]O2max), with a constant PVO2. During these maneuvers the diffusion conductance, DCO2 ([latin capital V with dot above]O2/PVO2), changed with [latin capital V with dot above]O2. Raising the perfusion pressure/flow with a pump increased [latin capital V with dot above]O2 with a small rise in PVO2 so that DCO2 also increased. Removing tension from the muscle-between contractions elevated [latin capital V with dot above]O2 and DCO2 without a change in perfusion pressure. Hypoxemia decreased [latin capital V with dot above]O2 with a decrease in PVO2,; DCO2 remained constant. A three-compartment mathematical model, based on microsphere measurements of regional flow, was used to illustrate how regional flow variations may exist, and how they are poorly revealed in the mixed whole-muscle venous blood. The model shows [latin capital V with dot above]O2[middle dot]g-1 strongly related to flow. As [latin capital V with dot above]O2[middle dot]-1 increased as [Latin capital letter Q with dot above][middle dot]g-1 Increased, extraction decreased; and DCO2 increased.

(C)1995The American College of Sports Medicine