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Human muscle fascicle behavior in agonist and antagonist isometric contractions

Authors

  • Emilie M. Simoneau PhD,

    Corresponding author
    1. Laboratoire d'Automatique, de Mécanique, et d'Informatique industrielles et Humaines, FRE CNRS 3304, Université de Valenciennes et du Hainaut-Cambrésis, F-59313 Valenciennes Cedex 09, France
    • Laboratoire d'Automatique, de Mécanique, et d'Informatique industrielles et Humaines, FRE CNRS 3304, Université de Valenciennes et du Hainaut-Cambrésis, F-59313 Valenciennes Cedex 09, France
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  • Stefano Longo PhD,

    1. Universit` degli Studi di Milano, Milano, Italy
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  • Olivier R. Seynnes PhD,

    1. Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, UK
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  • Marco V. Narici PhD

    1. Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, UK
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Abstract

Introduction: The aim of this study was to compare, at a given level of electromyographic (EMG) activity, the behavior of dorsiflexor and plantarflexor muscles as assessed via their architecture (pennation angle and fiber length) during agonist or antagonist isometric contractions. Methods: Real-time ultrasonography and EMG activity of gastrocnemius medialis (GM) and tibialis anterior (TA) muscles were obtained while young males performed ramp isometric contractions in dorsi- and plantarflexion. Results: For both muscles, at a similar level of EMG activity, fiber length was longer, and pennation angle was smaller, during antagonist than during agonist contractions. Conclusions: These results indicate that, at similar levels of EMG activity, GM and TA muscles elicit a higher mechanical output while acting as an antagonist. These findings have important implications for muscle function testing. They show that estimation of antagonistic force using the common method based on the EMG/net torque relationship yields underestimated values. Muscle Nerve 45: 92–99, 2012

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