• da Silva CostaAndréia AbudAARibeirão Preto Medical School, Graduate Program in Rehabilitation and Functional Performance, University of São Paulo, Brazil; Biomechanics and Motor Control Lab, School of Physical Education and Sport of Ribeirão Preto, Univer, Tibor Hortobágyi, Rob den Otter, Andrew Sawers, and Renato Moraes.
• Ribeirão Preto Medical School, Graduate Program in Rehabilitation and Functional Performance, University of São Paulo, Brazil; Biomechanics and Motor Control Lab, School of Physical Education and Sport of Ribeirão Preto, University of São Paulo, Brazil; Department of Human Movement Sciences, University of Groningen Medical Center, Groningen, The Netherlands. Electronic address: andreia.costa@usp.br.
• Neuroscience. 2023 Sep 1; 527: 112111-21.

AbstractAge modifies walking balance and neuromuscular control. Cognitive and postural constraints can increase walking balance difficulty and magnify age-related differences. However, how such challenges affect neuromuscular control remains unknown. We determined the effects of age, cognitive task, and arm position on neuromuscular control of walking balance. Young (YA) and older adults (OA) walked on a 6-cm wide beam with and without arm crossing and a cognitive task. Walking balance was quantified by the distance walked on the beam. We also computed step speed, margin of stability, and cognitive errors. Neuromuscular control was determined through muscle synergies extracted from 13 right leg and trunk muscles. We analyzed neuromuscular complexity by the number of synergies and the variance accounted for by the first synergy, coactivity by the number of significantly active muscles in each synergy, and efficiency by the sum of the activation of each significantly active muscle in each synergy. OA vs. YA walked a 14% shorter distance, made 12 times more cognitive errors, and showed less complex and efficient neuromuscular control. Cognitive task reduced walking balance mainly in OA. Decreases in step speed and margin of stability, along with increased muscle synergy coactivity and reduced efficiency were observed in both age groups. Arm-crossing also reduced walking balance mostly in OA, but step speed decreased mainly in YA, in whom the margin of stability increased. Arm-crossing reduced the complexity of synergies. Age, cognitive task, and arm position affect differently muscle synergy recruitment but have similar effects on walking balance.Copyright © 2023 IBRO. Published by Elsevier Ltd. All rights reserved.

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