Abstract

The changes in composition of muscle interstitial fluid during severe exercise is discussed, and a study of the effect on muscle receptors of one such change, an increase in potassium ion concentration, is described. Results of experiments on rat muscle are presented which indicate that receptors in muscle are protected from great changes in potassium ion concentration by barrier membranes with structure and properties capable of adaptation in response to intensive muscular activity. The adaptation could delay the onset of receptor fatigue and muscle pain.