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: 2.75). 10/2009; 43(3):412-9. DOI: 10.1016/j.jbiomech.2009.10.009
Source: PubMed


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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    • "Thus, modules are suggested to allow the nervous system to produce consistent biomechanical functions. Given the specific sets of muscles investigated, four to five motor modules were sufficient to reconstruct a locomotor task with sufficient quality [36] [101] [168] [187]. Neptune et al. [187] described that body support was provided by Module 1 (hip and knee extensors, hip abductors) in early stance and Module 2 (plantarflexors) in late stance. "
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    • "g Frontiers in Computational Neuroscience | www . frontiersin . org 11 September 2015 | muscle excitation - driven musculoskeletal simulations of a large repertoire of human locomotion conditions ( also see Section Applicability of the developed MEP Model ) , a scientific area where the theory of muscle synergy is increasingly gaining importance ( McGowan et al . , 2010 ; Allen and Neptune , 2012 ; Rückert and d ' Avella , 2013 ; Sartori et al . , 2013 ; Gopalakrishnan et al . , 2014 ; Walter et al . , 2014 ) ."
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    • "Thus, modules are suggested to allow the nervous system to produce consistent biomechanical functions. Given the specific sets of muscles investigated, four to five motor modules were sufficient to reconstruct a locomotor task with sufficient quality [36] [101] [168] [187]. Neptune et al. [187] described that body support was provided by Module 1 (hip and knee extensors, hip abductors) in early stance and Module 2 (plantarflexors) in late stance. "

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