Muscle Activation in Specific Regions of the Trapezius During Modified Kendall Manual Muscle Tests

Abstract

Context: Manual muscle tests (MMTs) are often used when assessing shoulder injuries. For the trapezius, individual MMTs are used to selectively test the upper trapezius region (UTR), middle trapezius region (MTR), and lower trapezius region (LTR). The MMTs for each region are assumed to preferentially recruit the corresponding muscle fibers and produce a maximal contraction; however, whether this is true is unknown. Objective: To determine if maximal voluntary isometric contractions (MVICs) for the upper trapezius (UT-MVIC), middle trapezius (MT-MVIC), and lower trapezius (LT-MVIC), adapted from the Kendall MMTs, recruited the corresponding trapezius regions. Design: Crossover study. Setting: Laboratory. Patients or Other Participants: A total of young, healthy individuals (10 men, 9 women, 1 not listed; age = 23.9 ± 1.7 years, height = 171.4 ± 9.6 cm, mass = 75.7 ± 11.6 kg). Intervention(s): Participants performed 3 repetitions of each MVIC. High-density surface electromyography measurements were collected from the UTR, MTR, and LTR. Main Outcome Measure(s): Root mean square (excitation) of the UTR, MTR, and LTR. Results: We observed an increase in UTR excitation during the LT-MVIC compared with the UT-MVIC (P =.016) and MT-MVIC (P