Voluntary rate of torque development is impaired after a voluntary versus tetanic conditioning contraction

Authors

  • Cameron B. Smith BSc,

    1. School of Kinesiology, Arthur and Sonia Labatt Health Sciences Building, University of Western Ontario, London, Ontario, Canada
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  • Matti D. Allen MSc,

    1. School of Kinesiology, Arthur and Sonia Labatt Health Sciences Building, University of Western Ontario, London, Ontario, Canada
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  • Charles L. Rice PhD

    Corresponding author
    1. School of Kinesiology, Arthur and Sonia Labatt Health Sciences Building, University of Western Ontario, London, Ontario, Canada
    2. Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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  • This study was supported by the National Science and Engineering Research Council of Canada.

ABSTRACT

Introduction: Both voluntary and evoked conditioning contractions will potentiate muscle twitch contractile properties. The response of a voluntary contraction to each condition type is not well understood but it may be a more functional model than evoked twitch potentiation. Methods: Baseline measurements from tibialis anterior included: maximal isometric twitch torque and rate of torque development (RTD); maximal evoked 50-Hz torque; and maximal voluntary ballistic RTD. Potentiation was induced by a 10-s voluntary or tetanic contraction (∽78% MVC), followed by 2 twitches and 2 ballistic contractions. Results: Twitch properties (torque and RTD) were potentiated equally after each conditioning contraction. Ballistic RTD was greater post-tetanus (390.2 ± 59.3 Nm/s) than post-voluntary (356.4 ± 69.1 Nm/s), but both were reduced from baseline (422.0 ± 88.9 Nm/s). Conclusions: Twitch potentiation was similar between conditioning contraction types, but ballistic RTD was lower after post-tetanus than post-voluntary. The results indicate central inhibition or fatigue concurrent with peripheral potentiation. Muscle Nerve 49: 218–224, 2014

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