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Motor Control: A Conceptual Framework for Rehabilitation

Mindy F. Levin and Daniele Piscitelli

There is a lack of conceptual and theoretical clarity among clinicians and researchers regarding the control of motor actions based on the use of the term “motor control.” It is important to differentiate control processes from observations of motor output to improve communication and to make progress in understanding motor disorders and their remediation. This article clarifies terminology related to theoretical concepts underlying the control of motor actions, emphasizing how the term “motor control” is applied in neurorehabilitation. Two major opposing theoretical frameworks are described (i.e., direct and indirect), and their strengths and pitfalls are discussed. Then, based on the proposition that sensorimotor rehabilitation should be predicated on one comprehensive theory instead of an eclectic mix of theories and models, several solutions are offered about how to address controversies in motor learning, optimality, and adaptability of movement.

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Volume 26 (2022): Issue 3 (Jul 2022)

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Kinematic and Electromyography Responses to Increasing Proprioception Demand and a Lack of Visual Feedback in Healthy, Middle-Aged Women Tested on an Unstable Platform

Ewa Szczerbik, Malgorzata Kalinowska, and Malgorzata Syczewska

The purpose of the study was to investigate which changes in kinematics and muscle activity in healthy, middle-aged women are introduced to maintain balance on an unstable platform. Biodex Balance System tests were used in stable and unstable modes (sudden with eyes open/closed and gradual with eyes open). Simultaneously, lower-extremity kinematics and surface electromyography of back and legs muscles were captured. The dependence between balance scores, movement ranges, and root mean square of electromyography was assessed with multiple regression to evaluate the strategy used. The results showed multisegmental movements in sudden instability, and activity of at least one of the following muscles: gluteus maximus, erector spinae, and soleus in all conditions. Best balance scores were achieved when movements appeared in pelvis in transverse, and hip in frontal planes, worst when in pelvis in frontal, hip, and ankle in sagittal planes, and when mentioned muscles were activated. Further research is needed to identify the determinants of strategy choice.

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Addition of a Cognitive Task During Walking Alters Lower Body Muscle Activity

Jordyn Vienneau, Sandro Nigg, and Benno M. Nigg

This study compared electromyography of five leg muscles during a single walking task (WALK) to a dual task (walking + cognitive task; COG) in 40 individuals (20 M and 20 F) using a wavelet analysis technique. It was hypothesized that muscle activation during the dual task would differ significantly from the walking task with respect to both timing (H1) and frequency (H2). The mean overall intensity for the COG trials was 4.1% lower for the tibialis anterior and 5.5% higher for the gastrocnemius medialis than in the WALK trials. The changes between the WALK and COG trials were short 50 ms bursts that occurred within 100 ms of heel strike in the tibialis anterior, and longer activation periods during the stance phase in the gastrocnemius medialis. No changes in overall intensity were observed in the peroneus longus, gastrocnemius lateralis, or soleus. Furthermore, no clear frequency bands within the signal could further characterize the overall changes in muscle activity during the COG task. This advances our understanding of how the division of attentional resources affects muscle activity in a healthy population of adults.

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Postural Control Adaptations in Yoga Single-Leg Support Postures: Comparison Between Practitioners and Nonpractitioners

Dafne Pires Pinto, Pedro Vieira Sarmet Moreira, and Luciano Luporini Menegaldo

This paper investigates whether a group of regular Yoga practitioners shows postural control differences compared with healthy controls while performing single-leg Yoga postures. Ten Yoga practitioners were compared with a control group of 10 nonpractitioners performing two single-leg support Yoga postures: Vrksasana (tree posture) and Natarajasana (dancer posture). Rambling and trembling decomposition of the center of pressure trajectories was implemented using a genetic algorithm spectral optimization that avoids using horizontal forces and was validated with bipedal posture data. Additionally, the center of mass was estimated from body kinematics using OpenSim and compared with the rambling outputs. During Natarajasana, no postural control adaptations were observed. For Vrksasana, the Yoga practitioners showed a lower center of pressure ellipse confidence interval area, center of pressure anteroposterior SD, and smaller rambling SD in the mediolateral direction, suggesting possible supraspinal feed-forward motor adaptations associated with Yoga training.

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Prefrontal Cortex Brain Activation During Texting and Walking: A Functional Near-Infrared Spectroscopy Feasibility Study

Tal Krasovsky, Rawda Madi, Eyal Fruchter, Elias Jahjah, and Roee Holtzer

Texting while walking is an increasingly common, potentially dangerous task but its functional brain correlates have yet to be reported. Therefore, we evaluated prefrontal cortex (PFC) activation patterns during single- and dual-task texting and walking in healthy adults. Thirteen participants (29–49 years) walked under single- and dual-task conditions involving mobile phone texting or a serial-7s subtraction task, while measuring PFC activation (functional near-infrared spectroscopy) and behavioral task performance (inertial sensors, mobile application). Head lowering during texting increased PFC activation. Texting further increased PFC activation, and decreased gait performance similarly to serial-7 subtraction. Our results support the key role of executive control in texting while walking.

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Range of Motion Remains Constant as Movement Rate Decreases During a Repetitive High-Speed Knee Flexion–Extension Task

José Pedro Correia, João R. Vaz, Erik Witvrouw, and Sandro R. Freitas

Maintaining the range of motion in repetitive movement tasks is a crucial point since it directly influences the movement rate. Ensuring the movement amplitude can be reliably maintained when motor function is assessed by measuring the maximum movement rate is therefore a key consideration. However, the performed range of motion during such tasks is often not reported. This study aimed to determine whether individuals are able to maintain an intended range of motion during a knee flexion/extension maximum movement rate task in the absence of tactile and visual feedback. Twelve healthy male individuals performed knee flexion/extension at maximum speed for eight 10-s blocks in a 45° arc between 45° and 90°. The range of motion was monitored using a marker system and the movement rate was measured. The performed range of motion was not significantly different from the 45° arc during the task despite a 13.47% decrease in movement rate from the start to the end of the task. Nevertheless, there was only anecdotal evidence of no difference from 45° in most blocks, while on the second and seventh blocks, there was anecdotal evidence of differences in the Bayesian one-sample test. There was also no significant shift in the maximum flexion/extension angles throughout the task. Healthy male individuals were thus able to perform a consistent average predefined knee range of motion in a maximum movement rate task despite decreases in movement rate. This was achieved without constraint-inducing devices during the task, using only basic equipment and verbal feedback.

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Reaching Movements With Limb-Based Visual Feedback

Fatemeh Zahed and Max Berniker

Reaches in experimental settings are commonly found to be straight. This straightness is robust to physical, but not visual, perturbations. Here, we question whether typical visual feedback contributes to this finding by implicitly promoting straight movements. To do so, we replaced the conventional feedback depicting the hand’s location with feedback depicting the limb’s orientation. Reaching movements with three different visual feedback conditions were examined. In the final condition, the subject’s arm was depicted as two rotating links, and targets were depicted as two links indicating a desired arm posture. We found that by replacing standard cursor feedback, reaches became curved and arched to the target. Our findings further demonstrate that depicted feedback influences movements, and feedback depicting the limb, in particular, may elicit curved reaches.

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Examining the Mechanisms of Internal and External Focus of Attention With Donders’ Subtractive Method

Jarrod Blinch, John R. Harry, Melanie A. Hart, and Denis Cousineau

The goal of the current study was to measure the processing demands on the stages of information processing with internal and external foci of attention. Participants completed simple and two-choice reaction time tasks with internal and external foci of attention. Donders’ subtraction method was used to isolate the cumulative duration of stages unique to simple and choice reaction time tasks. Mean reaction time was comparable with internal and external foci of attention in simple and two-choice reaction time tasks. These results suggest that processing demands were comparable with internal and external foci of attention. We hypothesize that there was not a processing advantage for an external focus in simple reaction time because the required movements had low movement complexity.

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Young Swimmers’ Classification Based on Performance and Biomechanical Determinants: Determining Similarities Through Cluster Analysis

Jorge E. Morais, Tiago M. Barbosa, Henrique P. Neiva, Mario C. Marques, and Daniel A. Marinho

The aim of this study was to classify and identify young swimmers’ performance, and biomechanical determinant factors, and understand if both sexes can be clustered together. Thirty-eight swimmers of national level (22 boys: 15.92 ± 0.75 years and 16 girls: 14.99 ± 1.06 years) were assessed. Performance (swim speed at front crawl stroke) and a set of kinematic, efficiency, kinetic, and hydrodynamic variables were measured. Variables related to kinetics and efficiency (p < .001) were the ones that better discriminated the clusters. All three clusters included girls. Based on the interaction of these determinant factors, there are girls who can train together with boys. These findings indicate that not understanding the importance of the interplay between such determinants may lead to performance suppression in girls.