Loading rate and contraction duration effects on in vivo human Achilles tendon mechanical properties |
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| Authors: | Christopher McCrum Kai D Oberländer Gaspar Epro Peter Krauss Darren C James Neil D Reeves Kiros Karamanidis |
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| Affiliation: | 1. Department of Human Movement Science, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands;2. Institute of Movement and Sport Gerontology, German Sport University Cologne, Cologne, Germany;3. Media School, Fresenius University of Applied Science, Cologne, Germany;4. Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London, UK;5. Faculty of Science and Engineering, School of Healthcare Science, Manchester Metropolitan University, Manchester, UK |
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| Abstract: | Tendons are viscoelastic, which implies loading rate dependency, but loading rates of contractions are often not controlled during assessment of human tendon mechanical properties in vivo. We investigated the effects of sustained submaximal isometric plantarflexion contractions, which potentially negate loading rate dependency, on the stiffness of the human Achilles tendon in vivo using dynamometry and ultrasonography. Maximum voluntary contractions (high loading rate), ramp maximum force contractions with 3 s loading (lower loading rate) and sustained contractions (held for 3 s) at 25%, 50% and 80% of maximal tendon force were conducted. No loading rate effect on stiffness (25–80% max. tendon force) was found. However, loading rate effects were seen up to 25% of maximum tendon force, which were reduced by the sustained method. Sustained plantarflexion contractions may negate loading rate effects on tendon mechanical properties and appear suitable for assessing human Achilles tendon stiffness in vivo. |
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| Keywords: | gastrocnemius muscle M triceps surae muscle strength tendon stiffness tendon strain ultrasonography |
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