![]() ![]() Perturbations to walking can elicit long-latency muscle responses ( Tang et al., 1998 Chvatal and Ting, 2012) as well as alter the locomotor rhythm during stumbling corrective responses ( Pijnappels et al., 2005 van Der Linden et al., 2007). ![]() These patterns can be modified by sensory feedback ( Forssberg et al., 1980 Quevedo et al., 2000 Rossignol and Bouyer, 2004) and motor planning mechanisms ( Drew et al., 2002) that alter the gait pattern. Neural circuits for locomotion have been identified in the mammalian spinal cord, and can endogenously produce rhythmic motor patterns to muscles ( Brown, 1911 Grillner, 1975 Rossignol et al., 1996). However, little is known about how the nervous system integrates the concurrent control of locomotion and balance functions over different movement contexts. Achieving these remarkable behaviors requires precise and dynamic coordination of multiple muscles across the limbs and trunk via hierarchical neural pathways. Humans and animals are able to robustly move over diverse terrains and withstand challenging disturbances to balance during locomotion. Muscle synergy analysis may also provide a more generalizable assessment of motor function by identifying whether common modular mechanisms are impaired across the performance of multiple motor tasks. temporal organization of muscle activity in motor deficits. Muscle synergy analysis may aid in dissociating deficits in spatial vs. Thus, muscle synergies specifying spatial organization of muscle activation patterns may define a repertoire of biomechanical subtasks available to different neural circuits governing walking and reactive balance and may be recruited based on task-level goals. For example, muscle synergies specific to walking perturbations may reflect biomechanical challenges associated with single limb stance, and muscle synergies used during sagittal balance recovery in standing but not walking were consistent with maintaining the different desired center of mass motions in standing vs. Differences in muscle synergies across conditions reflected differences in the biomechanical demands of the tasks. We also show that most muscle synergies using in reactive balance were also used during unperturbed walking, suggesting that neural circuits mediating locomotion and reactive balance recruit a common set of muscle synergies to achieve task-level goals. We show that most muscle synergies used in perturbations responses during standing were also used in perturbation responses during walking, suggesting common neural mechanisms for reactive balance across different contexts. In humans, we examined muscle activity during multidirectional support-surface perturbations during standing and walking, as well as unperturbed walking at two speeds. Here, we hypothesized that reactive balance and walking are mediated by a common set of lower-limb muscle synergies. Muscle synergies have been studied independently in standing balance and walking, but not compared. Little is known about the integration of neural mechanisms for balance and locomotion. Coulter Department of Biomedical Engineering, Georgia Tech and Emory University, Atlanta, GA, USA ![]()
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