Paired changes in electromechanical delay and musculo-tendinous stiffness after endurance or plyometric training

  • Jean-Francois Grosset
  • Julien Piscione
  • Daniel Lambertz
  • Chantal Pérot
Original Article


When measured in vivo electromechanical delay (EMD) depends mainly on the elastic properties of the muscle–tendon unit. Recent studies have shown changes in stiffness of the triceps surae (TS) following a period of training. To confirm the influence of musculo-tendinous stiffness on EMD, this study investigates paired changes in these two parameters after a training period. Two types of training known to induce opposite changes in stiffness were analysed. EMD and musculo-tendinous stiffness were measured on adult subjects before and after 10 weeks of endurance (n = 21) or plyometric (n = 9) trainings. EMD was defined as the time lag between the TS M-wave latency and the onset of muscle twitch evoked at rest by supramaximal electrical stimulations of the posterior tibial nerve. Quick release tests were used to evaluate the musculo-tendinous stiffness of the ankle plantar flexors. The stiffness index was defined as the slope of the relationship between angular stiffness and external torque values. Endurance training, known to preferentially activate the slow, stiffer muscle fibers, leads to a decrease in EMD and to an increase in stiffness index. Following plyometric training, which specifically recruits fast, more compliant fibers, EMD and the stiffness index exhibited adaptations directionally opposite to those seen with endurance training. When pooling the data for the two subject groups, a correlation was found between changes in EMD and changes in musculo-tendinous stiffness indexes. Thus, changes in EMD values are proposed to indirectly link to changes in musculo-tendinous stiffness for subjects involved in muscle training.


Electromechanical delay Musculo-tendinous stiffness Endurance training Plyometric training 



We thank the students who took part in this study. This study was supported by grants from the Centre National d’Etudes Spatiales (CNES) and the Pôle GBM Périnatalité-Enfance de la Région Picardie. The English text was edited by Dr. Owen Parkes and Dr. Gladys Onambele-Pearson.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Jean-Francois Grosset
    • 1
  • Julien Piscione
    • 1
  • Daniel Lambertz
    • 1
  • Chantal Pérot
    • 1
  1. 1.CNRS UMR 6600 Biomécanique et BioingénierieUniversité de Technologie de CompiègneCompiègne CedexFrance

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