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 pathologies. For the trapezius, individual MMTs are used to selectively test the upper (UTR), middle (MTR), and lower (LTR) trapezius regions. It is assumed that MMTs for each region preferentially recruit the corresponding muscle fibres and produce a “maximal” contraction; however, it is unknown if this is true. Objective: To determine if maximum voluntary isometric contractions (MVICs) for the upper (UT-MVIC), middle (MT-MVIC), and lower (LT-MVIC) trapezius, adapted from the Kendall MMTs, recruit the corresponding trapezius regions. Design: Cross-Over. Setting: Laboratory. Participants: 20 young, healthy individuals. Intervention: Participants performed three repetitions of each MVIC. High density surface electromyography was collected from the UTR, MTR, and LTR. Main Outcome Measures: Root mean square (excitation) of the UTR, MTR, and LTR. Statistical Analysis: Three, one-way repeated measures ANOVAs. Results: UTR excitation: There was a significant increase in UTR excitation during the LT-MVIC compared to the UT-MVIC (p = .016), and MT-MVIC (p < .001). MTR excitation: There was a significant increase in MTR excitation during the MT-MVIC compared to the UT-MVIC (p = .001), and a significant increase in MTR excitation during the LT-MVIC compared to the UT-MVIC (p < .001). There was also a significant increase in MTR excitation during the LT-MVIC compared to the MT-MVIC (p < .001). LTR excitation: There was a significant increase in LTR excitation during the MT-MVIC (p < .001) and LT-MVIC (p < .001) compared to the UT-MVIC. Conclusions: The UT-MVIC and MT-MVIC do not necessarily recruit the corresponding trapezius regions more than the other MVICs. Rather, the LT-MVIC appears to produce the greatest excitation in all trapezius regions. Additional research is needed; however, clinicians should be aware that maximal contractions may not always recruit the desired musculature when forming a clinical interpretation.

Baseline Has no Effect on Change in Forward Shoulder Posture, Range of Motion, and Muscle Excitation Following Myofascial Release: A Velocity-dependent Investigation

“…Compared to individual test positions for the UT and MT, the LT MVC position provides the greatest excitation for all three regions of the trapezius and was therefore used for the trapezius MVC. For the PEC MVC, participants attempted to horizontally adduct the handle while lying supine on the plinth with their shoulder abducted at 90 ° [13]. For all MVCs, a 5-second countdown was provided, and participants were directed to contract as hard as possible for 5 seconds using the targeted muscles.…”