Muscle-tendon interaction and elastic energy usage in human walking

1 Department of Biology of Physical Activity, Neuromuscular Research Center, University of Jyväskylä, Jyväskylä, Finland; 2 Department of Health Science and Technology, Clinic of Surgery, Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark; 3 Central Hospital of Central Finland, Jyväskylä, Finland; and 4 Institute for Biomechanics, German Sport University of Cologne, Cologne, Germany Submitted 16 February 2005 ; accepted in final form 19 April 2005 The present study was designed to explore how the interaction between the fascicles and tendinous tissues is involved in storage and utilization of elastic energy during human walking. Eight male subjects walked with a natural cadence (1.4 ± 0.1 m/s) on a 10-m-long force plate system. In vivo techniques were employed to record the Achilles tendon force and to scan real-time fascicle lengths for two muscles (medial gastrocnemius and soleus). The results showed that tendinous tissues of both medial gastrocnemius and soleus muscles lengthened slowly throughout the single-stance phase and then recoiled rapidly close to the end of the ground contact. However, the fascicle length changes demonstrated different patterns and amplitudes between two muscles. The medial gastrocnemius fascicles were stretched during the early single-stance phase and then remained isometrically during the late-stance phase. In contrast, the soleus fascicles were lengthened until the end of the single-stance phase. These findings suggest that the elastic recoil takes place not as a spring-like bouncing but as a catapult action in natural human walking. The interaction between the muscle fascicles and tendinous tissues plays an important role in the process of release of elastic energy, although the leg muscles, which are commonly accepted as synergists, do not have similar mechanical behavior of fascicles in this catapult action. tendinous tissue; soleus; medial gastrocnemius Address for reprint requests and other correspondence: M. Ishikawa, Neuromuscular Research Center, Dept. of Biology of Physical Activity, Univ. of Jyväskylä, PO Box 35 (LL2), 40014 Jyväskylä, Finland (E-mail: masaki{at}sport.jyu.fi )