An Electromyographic Technique for Comparing the Relative Involvement of Skeletal Muscles During Exercise

Abstract

One fundamental limitation in the exercise specialist's ability to prescribe the most effective conditioning or rehabilitation exercise for a particular individual is his understanding of the exact muscular demands of each exercise. Researchers interested in conditioning and therapeutic exercises have found the myo-electric signal a useful diagnostic tool for determining phasic action, and for subjectively assessing the tension levels of participating muscles. It is now generally accepted that the electrical activity in human skeletal muscle bears a linar relation to the tension being exerted during an isometric contraction when experimental conditions are strictly standardized. This relationship also applies to a muscle shortening at a constant velocity.

Despite the obvious advantages in knowing the quantitative involvement of specific skeletal muscles in various exercises, most of the research has been confined to subjective assessment of action potentials. On the basis that the integrated myo-electric signal can be displayed as a deviation from the baseline proportional to the strength and duration of muscle contraction, a technique was developed in an attempt to permit a comparison of the quantitative involvement of a specific muscle for various exercises.

This paper describes the instrumentation and technique employed as well as some initial observations obtained when six shoulder and arm muscles of 40 subjects were compared for ten different variations of the shoulder flexion - elbow extension movement.