In vivo behavior of the human soleus muscle with increasing walking and running speeds

The interaction between the muscle fascicle and tendon components of the human soleus (SO) muscle influences the capacity of the muscle to generate force and mechanical work during walking and running. In the present study, ultrasound-based measurements of in vivo SO muscle fascicle behavior were co...

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Bibliographic Details
Published in:Journal of applied physiology (1985) 2015-05, Vol.118 (10), p.1266-1275
Main Authors: Lai, Adrian, Lichtwark, Glen A, Schache, Anthony G, Lin, Yi-Chung, Brown, Nicholas A T, Pandy, Marcus G
Format: Article
Language:English
Subjects:
Adult
Ankle - physiology
Biomechanical Phenomena
Elasticity - physiology
Electromyography
Female
Humans
Joints - anatomy & histology
Joints - physiology
Male
Muscle Contraction - physiology
Muscle, Skeletal - anatomy & histology
Muscle, Skeletal - diagnostic imaging
Muscle, Skeletal - physiology
Muscular system
Running
Running - physiology
Tendons
Tendons - physiology
Torque
Ultrasonic imaging
Ultrasonography
Walking
Walking - physiology
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Summary:The interaction between the muscle fascicle and tendon components of the human soleus (SO) muscle influences the capacity of the muscle to generate force and mechanical work during walking and running. In the present study, ultrasound-based measurements of in vivo SO muscle fascicle behavior were combined with an inverse dynamics analysis to investigate the interaction between the muscle fascicle and tendon components over a broad range of steady-state walking and running speeds: slow-paced walking (0.7 m/s) through to moderate-paced running (5.0 m/s). Irrespective of a change in locomotion mode (i.e., walking vs. running) or an increase in steady-state speed, SO muscle fascicles were found to exhibit minimal shortening compared with the muscle-tendon unit (MTU) throughout stance. During walking and running, the muscle fascicles contributed only 35 and 20% of the overall MTU length change and shortening velocity, respectively. Greater levels of muscle activity resulted in increasingly shorter SO muscle fascicles as locomotion speed increased, both of which facilitated greater tendon stretch and recoil. Thus the elastic tendon contributed the majority of the MTU length change during walking and running. When transitioning from walking to running near the preferred transition speed (2.0 m/s), greater, more economical ankle torque development is likely explained by the SO muscle fascicles shortening more slowly and operating on a more favorable portion (i.e., closer to the plateau) of the force-length curve.
ISSN:8750-7587
1522-1601
DOI:10.1152/japplphysiol.00128.2015