[Relation of the duration of muscle action potentials to intramuscular temperature]

On 40 motor unit potentials recorded from the abductor digiti quinti muscle of 4 normal subjects the alteration of shape and duration under the influence of decreasing temperature (36 to 22 degrees C) has been examined. The mean increase of duration was about 6%/degrees C for the temperature range between 36 and 30 degrees C and about 9%/degrees C for the range between 30 and 22 degrees C. A significant alteration of shape, e.g. an increased incidence of polyphasic potentials as observed by Buchthal, could not be demonstrated. This prolongation of motor unit potential's duration probably results mainly from an increased temporal dispersion of impulse propagation in the terminal branches of motor nerve fibres and from a delayed impulse conduction over the muscle fibre membrane.