Muscle activation in specific regions of the trapezius during modified Kendall manual muscle tests.

Abstract

CONTEXT\nManual 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.\n\n\nOBJECTIVE\nTo 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.\n\n\nDESIGN\nCross-Over.\n\n\nSETTING\nLaboratory.\n\n\nPARTICIPANTS\n20 young, healthy individuals.\n\n\nINTERVENTION\nParticipants performed three repetitions of each MVIC. High density surface electromyography was collected from the UTR, MTR, and LTR.\n\n\nMAIN OUTCOME MEASURES\nRoot mean square (excitation) of the UTR, MTR, and LTR.\n\n\nSTATISTICAL ANALYSIS\nThree, one-way repeated measures ANOVAs.\n\n\nRESULTS\nUTR 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.\n\n\nCONCLUSIONS\nThe 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.