Plasticity of human Achilles tendon mechanical and morphological properties in response to cyclic strain |
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| Authors: | Adamantios Arampatzis Andreas Peper Stefanie Bierbaum Kirsten Albracht |
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| Institution: | 1. Humboldt-University Berlin, Department of Training and Movement Sciences, Philippstr. 13, Haus 11, 10115 Berlin, Germany;2. Centre of Sport Science and Sport Medicine Berlin (CSSB);3. Institute of Biomechanics and Orthopaedics, German Sport University Cologne;1. Department of Biomedical Engineering, University of Wisconsin-Madison, WI, USA;2. Department of Mechanical Engineering, University of Wisconsin-Madison, WI, USA;3. Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, WI, USA;1. Institute of Movement and Sport Gerontology, German Sport University Cologne, Cologne, Germany;2. Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Cologne, Germany;3. School of Science Department of Physics, National and Kapodistrian University of Athens, Athens, Greece;4. Faculty of Mathematics and Technology, University of Applied Sciences, Remagen, Germany;1. Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6;1. Department of Mechanical Engineering, Vanderbilt University, Nashville, TN, USA;2. Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA;3. Department of Physical Medicine & Rehabilitation, Vanderbilt University, Nashville, TN, USA;1. Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California, USA;2. Division of Physical Therapy, School of Medicine, West Virginia University, Morgantown, West Virginia, USA;3. Department of Biomechanics, University School of Physical Education in Wroclaw, Wroclaw, Poland;4. Department of Biological Systems Engineering, University of Nebraska–Lincoln, Lincoln, Nebraska, USA;1. Graduate School of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa-shi, Saitama 359-1192, Japan;2. Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa-shi, Saitama 359-1192, Japan;3. College of System Engineering and Science, Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama-shi, Saitama 337-0003, Japan;4. National Institute of Fitness and Sports in KANOYA, 1 Shiromizu-cho, Kanoya-shi, Kagoshima 891-2393, Japan |
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| Abstract: | The purpose of the current study in combination with our previous published data (Arampatzis et al., 2007) was to examine the effects of a controlled modulation of strain magnitude and strain frequency applied to the Achilles tendon on the plasticity of tendon mechanical and morphological properties. Eleven male adults (23.9±2.2 yr) participated in the study. The participants exercised one leg at low magnitude tendon strain (2.97±0.47%), and the other leg at high tendon strain magnitude (4.72±1.08%) of similar frequency (0.5 Hz, 1 s loading, 1 s relaxation) and exercise volume (integral of the plantar flexion moment over time) for 14 weeks, 4 days per week, 5 sets per session. The exercise volume was similar to the intervention of our earlier study (0.17 Hz frequency; 3 s loading, 3 s relaxation) allowing a direct comparison of the results. Before and after the intervention ankle joint moment has been measured by a dynamometer, tendon–aponeurosis elongation by ultrasound and cross-sectional area of the Achilles tendon by magnet resonance images (MRI). We found a decrease in strain at a given tendon force, an increase in tendon–aponeurosis stiffness and tendon elastic modulus of the Achilles tendon only in the leg exercised at high strain magnitude. The cross-sectional area (CSA) of the Achilles tendon did not show any statistically significant (P>0.05) differences to the pre-exercise values in both legs. The results indicate a superior improvement in tendon properties (stiffness, elastic modulus and CSA) at the low frequency (0.17 Hz) compared to the high strain frequency (0.5 Hz) protocol. These findings provide evidence that the strain magnitude applied to the Achilles tendon should exceed the value, which occurs during habitual activities to trigger adaptational effects and that higher tendon strain duration per contraction leads to superior tendon adaptational responses. |
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