Abstract

During vigorous, strong contractions there is a rapid decline in the mecha- nical output in skeletal muscle. Several studies have indicated that this rapid decline in force development (often referred to as fatique), is caused by metabolic changes in the muscles. During brief intense exercise there is a rapid breakdown of phosphocreatine and glycogen and a concomitant increase in the lactate and hydrogen ion concentration. The muscle lactate concentration is increased from about 1-2 mmol kg wet weight at rest before exercise to approximately 25-30 mmol kg wet weight immediately after intensive exercise. The muscle pH falls from about 7.0 at rest to approximately 6.4 at exhaustion.It is suggested that the changes in intracellular pH might affect the force generation of skeletal muscle by two different mechanisms: (1) The fall in intracellular pH reduces the activity of key enzymes in glycolysis, thus reducing the rate of ATP resynthesis, and (2) the increased hydrogen ion concentration has a direct effect on the contractile processes, thus reducing the rate of ATP utilization. It is suggested that the increased hydrogen ion concentration might be the common regulator for the maximal rate at which ATP is being utilized and the maximal rate at which it is being resynthesized. Verf.-Referat