JOINT REFLEXES AND REGULATION OF RESPIRATION DURING EXERCISE

Abstract

Respiratory responses to passive flexion of the hind limbs and to electrical stimulation of nerves to the knee joint were studied in a series of cats and dogs. Passive flexion is accompanied by variable changes in rate and depth of respiration. These changes do not appear to result from the stimulation of receptors in the knee joint because: Other types of stimuli, including those secondarily induced by the flexion, such as movements of the trunk, were as effective in stimulating respiration. Electrical stimulation was effective only at intensities great enough to activate slower conducting fibers, resulting in what appeared to be a pain hyperpnea. It is concluded that under the conditions of anesthesia used, joint reflexes do not play a significant role in the production of respiratory changes during passive flexion, and that there is no satisfactory evidence that limb reflexes are important in the regulation of respiration during exercise in man.