Article

Modular control of human walking: Adaptations to altered mechanical demands.

Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
Journal of biomechanics (impact factor: 2.66). 10/2009; 43(3):412-9. DOI:10.1016/j.jbiomech.2009.10.009 pp.412-9
Source: PubMed

ABSTRACT Studies have suggested that the nervous system may adopt a control scheme in which synergistic muscle groups are controlled by common excitation patters, or modules, to simplify the coordination of movement tasks such as walking. A recent computer modeling and simulation study of human walking using experimentally derived modules as the control inputs provided evidence that individual modules are associated with specific biomechanical subtasks, such as generating body support and forward propulsion. The present study tests whether the modules identified during normal walking could produce simulations of walking when the mechanical demands were substantially altered. Walking simulations were generated that emulated human subjects who had their body weight and/or body mass increased and decreased by 25%. By scaling the magnitude of five module patterns, the simulations could emulate the subjects' response to each condition by simply scaling the mechanical output from modules associated with specific biomechanical subtasks. Specifically, the modules associated with providing body support increased (decreased) their contribution to the vertical ground reaction force when body weight was increased (decreased) and the module associated with providing forward propulsion increased its contribution to the positive anterior-posterior ground reaction force and positive trunk power when the body mass was increased. The modules that contribute to controlling leg swing were unaffected by the perturbations. These results support the idea that the nervous system may use a modular control strategy and that flexible modulation of module recruitment intensity may be sufficient to meet large changes in mechanical demand.

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Keywords

body mass
 
body weight
 
common excitation patters
 
control inputs
 
emulated human subjects
 
generating body support
 
individual modules
 
mechanical demands
 
modular control strategy
 
module recruitment intensity
 
modules
 
positive trunk power
 
present study tests
 
recent computer modeling
 
simulations
 
specific biomechanical subtasks
 
subjects' response
 
synergistic muscle groups
 
vertical ground reaction force
 
Walking simulations