The minimum number of contractions required to examine the EMG amplitude versus isometric force relationship for the vastus lateralis and vastus medialis |
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| Institution: | 1. School of Health and Human Sciences, Southern Cross University, Lismore, NSW, Australia;2. Human Performance Laboratory, University of Calgary, Calgary, Alberta, Canada;1. Department of Physical Therapy, The Graduate School, Inje University, Republic of Korea;2. Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University, 607 Obangdong, Gimhae, Gyeongsangnamdo 621-749, Republic of Korea;1. Industrial and Management Systems Engineering, West Virginia University, PO Box 6070, Morgantown, WV 26506-6107, United States;2. Safety Sciences Department, Indiana University of Pennsylvania, 1011 South Drive, Indiana, PA 15705, United States;1. School of Life Science, Faculty of Science, Engineering and Computing, Kingston University, London, UK;2. Faculty of Health Science and Education, Kingston University/St George''s University of London, UK |
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| Abstract: | Studies have demonstrated that the electromyographic (EMG) amplitude versus submaximal isometric force relationship is relatively linear. The purpose of this investigation was to determine the minimum number of contractions required to study this relationship. Eighteen men (mean age = 23 years) performed isometric contractions of the leg extensors at 10–90% of the maximum voluntary contraction (MVC) in 10% increments while surface EMG signals were detected from the vastus lateralis and vastus medialis. Linear regression was used to determine the coefficient of determination, slope coefficient, and y-intercept for each muscle and force combination with successively higher levels included in the model (i.e., 10–30%, … 10–90% MVC). For the slope coefficients, there was a main effect for force combination (P < .001). The pairwise comparisons showed there was no difference from 10–60% through 10–90% MVC. For the y-intercepts, there were main effects for both muscle (vastus lateralis 4.3 μV RMS] > vastus medialis ?3.7 μV RMS]; P = .034) and force combination (P < .001), with similar values shown from 10–50% through 10–90% MVC. The linearity of the absolute EMG amplitude versus isometric force relationship for the vastus lateralis and vastus medialis suggests that investigators may exclude high force contractions from their testing protocol. |
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| Keywords: | EMG Muscle Motor unit |
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