Int J Sports Med 2016; 37(08): 647-652
DOI: 10.1055/s-0035-1564174
Training & Testing
© Georg Thieme Verlag KG Stuttgart · New York

Electromyographic Responses from the Vastus Medialis during Isometric Muscle Actions

C. M. Smith
1   Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, United States
,
T. J. Housh
1   Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, United States
,
T. Herda
2   Health, Sport and Exercise Science, University of Kansas, Lawrence, United States
,
J. M. Zuniga
3   Exercise Science, Creighton University, Omaha, United States
,
C. L. Camic
4   Exercise & Sport Science, University of Wisconsin – La Crosse, La Crosse, United States
,
H. C. Bergstrom
1   Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, United States
,
D. B. Smith
5   Health and Human Performance, Oklahoma State University, Stillwater, United States
,
J. P. Weir
2   Health, Sport and Exercise Science, University of Kansas, Lawrence, United States
,
J. T. Cramer
6   Department of Nutrition & Health Sciences, University of Nebraska-Lincoln, Lincoln, United States
,
E. C. Hill
7   Nutrition and Health Sciences, Ethan Hill, Lincoln, United States
,
K. C. Cochrane
1   Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, United States
,
N. D. M. Jenkins
1   Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, United States
,
R. J. Schmidt
1   Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, United States
,
G. Johnson
1   Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, United States
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accepted after revision 24. August 2015

Publikationsdatum:
13. Mai 2016 (online)

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Abstract

This study examined the electromyographic (EMG) responses from the vastus medialis (VM) for electrodes placed over and away from the innervation zone (IZ) during a maximal voluntary isometric contraction (MVIC) and sustained, submaximal isometric muscle action. A linear electrode array was placed on the VM to identify the IZ and muscle fiber pennation angle during an MVIC and sustained isometric muscle action at 50% MVIC. EMG amplitude and frequency parameters were determined from 7 bipolar channels of the electrode array, including over the IZ, as well as 10 mm, 20 mm and 30 mm proximal and distal to the IZ. There were no differences between the channels for the patterns of responses for EMG amplitude or mean power frequency during the sustained, submaximal isometric muscle action; however, there were differences between channels during the MVIC. The results of the present study supported the need to standardize the placement of electrodes on the VM for the assessment of EMG amplitude and mean power frequency. Based on the current findings, it is recommended that electrode placements be distal to the IZ and aligned with the muscle fiber pennation angle during MVICs, as well as sustained, submaximal isometric muscle actions.