Conduction velocity in ischemic muscle: effect on EMG frequency spectrum.

MORTIMER, J. THOMAS, ROBERT MAGNUSSON, AND INGEMAR PETERSON. Conduction velocity in ischemic muscle: effect or2 EMG frequency spectrum. Am. J. Physiol. 219(5): 1324-1329. 1970.-The action-potential conduction velocity in Yed” and “white” muscles was studied. The study was made by recording the conduction times during and following periods of repeated contractions while the muscle was ischemic or perfused with a dextran solution. During ischemia, repeated stimulation resulted in a continuous decay in the propagation velocity of the action potential. The decrease in conduction velocity is more pronounced in the gastrocnemius than in the soleus. The measured changes in conduction velocity are sufficient to account for changes in the EMG frequency spectrum noticed during muscle fatigue. Prolonged stimulation of a dextran-perfused muscle resulted in a significantly smaller change in conduction velocity than the change found in the ischemic experiment. It was concluded that maintenance of normal conduction velocity is dependent on the blood flow for removal of metabolic by-products and not for an energy supply. The metabolic by-product causing the velocity changes is suspected to be lactic acid.