Muscle blood flow and distribution determine maximal VO2 of contracting muscle

• Published in: Medicine and science in sports and exercise 1995-01, Vol.27 (1), p.43-46
• Main Authors: Stainsby, W N, Brechue, W F, Ameredes, B T
• Format: Article
• Language: English
• Subjects: Animals; Blood Pressure - physiology; Blood Vessels - physiology; Diffusion; Dogs; Hemoglobins - metabolism; Hypoxia - physiopathology; Ischemia - physiopathology; Mathematics; Microspheres; Models, Biological; Muscle Contraction - physiology; Muscle Relaxation - physiology; Muscle, Skeletal - blood supply; Muscle, Skeletal - metabolism; Oxygen - blood; Oxygen Consumption - physiology; Regional Blood Flow - physiology; Space life sciences
• ISSN: 0195-9131
• DOI: 10.1249/00005768-199501000-00009

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 VO2max with a constant PVO2. During these maneuvers the diffusion conductance, DCO2 (VO2/PVO2), changed with VO2. Raising the perfusion pressure/flow with a pump increased VO2 with a small rise in PVO2 so that DCO2 also increased. Removing tension from the muscle between contractions elevated VO2 and DCO2 without a change in perfusion pressure. Hypoxemia decreased VO2 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 VO2.g-1 strongly related to flow. As VO2.g-1 increased as Q.g-1 increased, extraction decreased, and DCO2 increased.