Synergies Stabilizing Vertical Posture in Spaces of Control Variables

Nardon, Mauro; Pascucci, Francesco; Cesari, Paola; Bertucco, Matteo; Latash, Mark L.

doi:10.1016/j.neuroscience.2022.08.006

Cited by 17 publications

(2 citation statements)

References 70 publications

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“…In each plot, the length of the radial segment indicates the r 2 value of the cosine fit of the dependence of amplitude coefficients on pulling direction and Latash 2000;Piscitelli et al 2017;Bertucco et al 2021;Cesari et al 2022). Accordingly, it has recently been proposed that posture-stabilizing strategies could emerge from a co-existence of muscle reciprocal activations, which indicate the spontaneous migration of the CoP leading to the rambling component of postural sway, and muscle cocontraction levels that adjust as needed to ensure postural stability resulting, as whole, in strong co-variation of referent body configurations and apparent stiffness (Nardon et al 2022). In this regards, our results of varied levels of directional tuning amplitudes from distinctive muscle synergies could reflect the coexistence of diversified neuromechanical strategies to ensure stable postures in the multi-joint system, through the control of co-contraction levels, while controlling the multidirectional fluctuations of the CoP by muscle reciprocal activations to counteract forces applied to the body in order to maintain balance in quiet standing posture (Imagawa et al 2013;Kubo et al 2017;Piscitelli et al 2017).…”

Section: Muscle Synergies Similarity Across Participantsmentioning

confidence: 99%

Muscle synergies for multidirectional isometric force generation during maintenance of upright standing posture

Monte,

Benamati,

Pavan

et al. 2024

Exp Brain Res

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Muscle synergies are defined as coordinated recruitment of groups of muscles with specific activation balances and time profiles aimed at generating task-specific motor commands. While muscle synergies in postural control have been investigated primarily in reactive balance conditions, the neuromechanical contribution of muscle synergies during voluntary control of upright standing is still unclear. In this study, muscle synergies were investigated during the generation of isometric force at the trunk during the maintenance of standing posture. Participants were asked to maintain the steady-state upright standing posture while pulling forces of different magnitudes were applied at the level at the waist in eight horizontal directions. Muscle synergies were extracted by nonnegative matrix factorization from sixteen lower limb and trunk muscles. An average of 5-6 muscle synergies were sufficient to account for a wide variety of EMG waveforms associated with changes in the magnitude and direction of pulling forces. A cluster analysis partitioned the muscle synergies of the participants into a large group of clusters according to their similarity, indicating the use of a subjective combination of muscles to generate a multidirectional force vector in standing. Furthermore, we found a participant-specific distribution in the values of cosine directional tuning parameters of synergy amplitude coefficients, suggesting the existence of individual neuromechanical strategies to stabilize the whole-body posture. Our findings provide a starting point for the development of novel diagnostic tools to assess muscle coordination in postural control and lay the foundation for potential applications of muscle synergies in rehabilitation.

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Section: Muscle Synergies Similarity Across Participantsmentioning

confidence: 99%

Muscle synergies for multidirectional isometric force generation during maintenance of upright standing posture

Monte,

Benamati,

Pavan

et al. 2024

Exp Brain Res

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“…On the other hand, effects of dominance have been described for multi-finger synergies but not for multi-MU-mode synergies 22 . At the other end of the spectrum, analysis of performancestabilizing synergies at the task level using mechanical variables reflecting the R and C commands has documented such synergies over a range of tasks, from single-finger pressing to whole-body standing 23,24 .…”

Section: Introductionmentioning

confidence: 99%

Mini-review: Biological Movements as Objects of Natural Science

Latash

2023

BJMB

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BACKGROUND: Two approaches to biological movement have dominated the field, the computational approach (internal models) and the approach based on laws of nature pioneered by several researchers including Michael Turvey. AIM AND METHOD: We review a body of literature exploring and expanding the approach based on laws of nature. We show, in particular, how this approach fits the philosophical traditions of Merleau-Ponty, the theory of control with spatial referent coordinates, the principle of abundance, and the concept of performance-stabilizing synergies using the uncontrolled manifold hypothesis. RESULTS: Currently, this scheme of motor control has been applied successfully in studies of a variety of effectors, from single motor units to the whole body, a variety of tasks, and various populations. It led to the discovery of new phenomena and new interpretations of known phenomena. It has been productive in studies of neurological patients offering new understanding of some of the common pathologies (e.g., spasticity) and new tools for early diagnosis of various subcortical disorders and monitoring treatment effects. CONCLUSION: Currently, this field faces a number of challenges including the following: Mapping steps in the hierarchical control scheme on neurophysiological structures and circuits, understanding the relative role of intra-muscle (spinal) and multi-effector (supraspinal) synergies, expanding studies of movements in intact animals and animal preparation, and moving beyond the current scheme to fields traditionally associated with psychology. Just like the current scheme represents moving “outside the box” of classical mechanics, a step outside the current thinking is needed.

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Postural adjustments to self-triggered perturbations under conditions of changes in body orientation

et al. 2023

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We studied anticipatory and compensatory postural adjustments (APAs and CPAs) associated with self-triggered postural perturbations in conditions with changes in the initial body orientation. In particular, we were testing hypotheses on adjustments in the reciprocal and coactivation commands, role of proximal vs. distal muscles, and correlations between changes in indices of APAs and CPAs. Healthy young participants stood on a board with full support or reduced support area and held a standard load in the extended arms. They released the load in a self-paced manned with a standard small-amplitude arm movement. Electromyograms of 12 muscles were recorded and used to compute reciprocal and coactivation indices between three muscle pairs on both sides of the body. The subject’s body was oriented toward one of three targets: straight ahead, 60° to the left, and 60° to the right. Body orientation has stronger effects on proximal muscle pairs compared to distal muscles. It led to more consistent changes in the reciprocal command compared to the coactivation command. Indices of APAs and CPAs showed positive correlations across conditions. We conclude that the earlier suggested hierarchical relations between the reciprocal and coactivation command could be task-specific. Predominance of negative or positive correlations between APA and CPA indices could also be task-specific.

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Synergies Stabilizing Vertical Posture in Spaces of Control Variables

Cited by 17 publications

References 70 publications

Muscle synergies for multidirectional isometric force generation during maintenance of upright standing posture

Muscle synergies for multidirectional isometric force generation during maintenance of upright standing posture

Mini-review: Biological Movements as Objects of Natural Science

Postural adjustments to self-triggered perturbations under conditions of changes in body orientation

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