Muscles actuate walking by providing vertical support and forward progression of the mass center. To quantify muscle contributions to vertical support and forward progression (i.e., vertical and fore-aft accelerations of the mass center) over a range of walking speeds, three-dimensional muscle-actuated simulations of gait were generated and analyzed for eight subjects walking overground at very slow, slow, free, and fast speeds. We found that gluteus maximus, gluteus medius, vasti, hamstrings, gastrocnemius, and soleus were the primary contributors to support and progression at all speeds. With the exception of gluteus medius, contributions from these muscles generally increased with walking speed. During very slow and slow walking speeds, vertical support in early stance was primarily provided by a straighter limb, such that skeletal alignment, rather than muscles, provided resistance to gravity. When walking speed increased from slow to free, contributions to support from vasti and soleus increased dramatically. Greater stance-phase knee flexion during free and fast walking speeds caused increased vasti force, which provided support but also slowed progression, while contralateral soleus simultaneously provided increased propulsion. This study provides reference data for muscle contributions to support and progression over a wide range of walking speeds and highlights the importance of walking speed when evaluating muscle function.
A database of walking simulations as described in Liu et al., Nov 2008 (J Biomechanics), available for download and use by others.
Our paper quantifies muscle contributions to vertical support and forward progression over a range of walking speeds. 3D muscle-actuated simulations of gait were generated and analyzed for 8 subjects walking overground at very slow, slow, free, and fast speeds. The three-dimensional muscle-actuated simulations are provided in this project.
This project contains 32 three-dimensional muscle-actuated simulations of human walking (8 children walking at 4 speeds each) described in our publication. These simulations can be reproduced, modified, shared, and analyzed using OpenSim, a freely available software framework for generating and analyzing muscle-actuated simulations of movement.
To download the simulations and associated documentation, please see the Downloads section of this project. The OpenSim software is not included in these downloads and is required for running or analyzing the simulations. Please see https://simtk.org/home/opensim for more information on OpenSim. These simulations were generated using OpenSim version 1.5, which is the software version we recommend to those using these simulations.