Electromyography Evaluation of Rotator Cuff Manual Muscle Tests

Abstract

Manual muscle tests (MMTs) are frequently used in clinical settings to evaluate a specific muscle’s function and strength in a position at which this muscle is believed to be most isolated from other synergists and antagonists. It is necessary for a muscle to be tested in a state of isolation (as much as is physiologically possible), as interpretation of strength and function can be compromised by the contributions of other active muscles. In the present study, electromyographic activation of 14 shoulder muscles was assessed in 12 males during 29 shoulder exertions. Maximal isolation ratios defined which of these exertions most isolated the rotator cuff muscles. Results confirmed the appropriateness of nine clinical MMTs in isolating the rotator cuff muscles, but suggested that several other exertions were equally appropriate in isolating these muscles. Forces produced during isolation exertions can be compared to patient exertions to promote more objective MMT grading.