title: In vivo behavior of the human soleus muscle with increasing walking and running speeds.
abstract: 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.
authors: Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria, Australia; Performance Science and Innovation, Australian Institute of Sport, Belconnen, Australian Capital Territory, Australia.
authors: Adrian
authors: A
authors: Lai
authors: Centre for Sensorimotor Performance, The School of Human Movement Studies, The University of Queensland, St. Lucia, Queensland, Australia; and.
authors: Glen A
authors: GA
authors: Lichtwark
authors: Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria, Australia;
authors: Anthony G
authors: AG
authors: Schache
authors: Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria, Australia;
authors: Yi-Chung
authors: YC
authors: Lin
authors: Performance Science and Innovation, Australian Institute of Sport, Belconnen, Australian Capital Territory, Australia.
authors: Nicholas A T
authors: NA
authors: Brown
authors: Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria, Australia; pandym@unimelb.edu.au.
authors: Marcus G
authors: MG
authors: Pandy
mesh_terms: D000328:Adult; D000842:Ankle / Q000502:physiology; D001696:Biomechanical Phenomena; D004548:Elasticity / Q000502:physiology; D004576:Electromyography; D005260:Female; D006801:Humans; D007596:Joints / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013710:Tendons / Q000502:physiology; D019415:Torque; D014463:Ultrasonography; D016138:Walking / Q000502:physiology*
keywords: force-length; force-velocity; gait; muscle fascicle; tendon; ultrasound imaging