Clinical Physiology: The Effect of Circulatory Occlusion on Isometric Exercise Capacity and Energy Metabolism of the Quadriceps Muscle in Man

Occlusion of the circulation to the quadriceps muscle for 20 min resulted in decreases in the muscle ATP and phosphorylcreatine (PC) contents of 1 and 32 per cent, respectively, and increases in ADP and AMP of 7 and 37 per cent. Decrease in PC was statistically significant after 4 min of occlusion, suggesting that the local intramuscular oxygen store was sufficiently depleted at this time as to be limiting to normal mitochondrial function. Pyruvate and lactate concentrations in muscle and the lactate to pyruvate ratio were significantly increased after 15 min of occlusion but not before. The calculated local oxygen store in the muscle was 2.0 mmol O2 - (kg dry muscle)-1. Local oxygen store depletion after 4 and 10 min of occlusion was estimated to be 40-50 and 90-100 per cent complete. Increasing time of pre-exercise occlusion resulted in decreased isometric endurance capacity. The observed decreases in endurance, however, were far greater than could be accounted for by any parallel decrease in the local muscle energy stores.