Relation Between Electromyographic Voltage and Load

¹ From the Department of Physical Medicine, Georgia Warm Springs Foundation, Warm Springs, Georgia

A study was made on 56 control biceps brachialis muscles of the relation between the electromyographic voltage (peak to peak measurements of the voltage difference between skin electrodes) and the load lifted in voluntary contraction. For loads from 1 to 64 ounces the regression equation of voltage on load gives a reliable description of the voltage-load relation. The voltage increment per ounce of load was found to be 6.7 microvolts with a standard error of 0.3 µv. The voltage intercept for load equal to zero was 133 µv. A similar survey was made of 214 poliomyelitis muscles. These were divided into three groups on the basis of strength. Regression equations gave a good fit to the data for each group. The slopes of the regression lines were: 25. ± 1.1, 42. ± 2.1 and 78. ± 8.7 in the order of strong to weak group. The voltage intercepts in the same order were: 475, 1048 and 866.