DURATION AND FORM OF ACTION POTENTIAL IN THE NORMAL HUMAN MUSCLE

Abstract

A method of recording the action potential of single functional units in muscle is described. Duration and amplitude varies with the 3 types of electrodes tested: (1) concentric needle electrode of Adrian and Bronk, duration 7.34 [plus or minus] 0.21 msec; (2) fine sewing needles coated except at the tip, duration 7.29 [plus or minus] 0.24 msec; (3) fine insulated wires inside a hypodermic needle, duration 2.01 [plus or minus]0.1 msec. The durations of types (1) and (2) are not significantly different. Amplitudes are smallest with type (3) and largest with type (2). The form is the same for all types, the most common being bi- and triphasic. Polycyclic potentials occur 2-4% of the time in the biceps brachii and interosseous muscles. Ten females and 20 males tested with type (1) had durations of 7.68 [plus or minus] 0.07 msec. in the first interosseous muscle, 7.56 [plus or minus] 0.14 msec. in the biceps brachii and 2.28 [plus or minus] 0.03 msec. in the facial muscles.