Learning effects on muscle modes and multi-mode postural synergies

Asaka, Tadayoshi; Wang, Yun; Fukushima, Junko; Latash, Mark L.

doi:10.1007/s00221-007-1101-2

Cited by 72 publications

(67 citation statements)

References 41 publications

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“…Note that a different "atypical" set of M-modes has been reported in studies when the subjects performed relatively natural tasks while standing on a board with a decreased support area (Krishnamoorthy et al 2004b;Asaka et al 2007). Those M-modes involved muscle cocontraction that could be interpreted as a change in the range of joint angle values within which the muscle pairs could be active simultaneously without a change in the body reference configuration.…”

Section: Hierarchical Control Of Posture and The Reference Configuratmentioning

confidence: 91%

“…Combined with previous reports, they also indicate that M-mode composition can vary in a task-specific way. Note that another group of M-modes, co-contraction modes, have been reported in studies of whole-body tasks performed in unusual conditions (Krishnamoorthy et al 2004); with practice, these M-modes tend to be replaced with "pushback" and "push-forward" modes (Asaka et al 2007). …”

Section: Composition Of Muscle Modesmentioning

confidence: 94%

“…At the upper level, the M-modes are considered as the elemental variables, and their co-variation is organized in a task-specific manner to stabilize an important performance variable. The idea of a two-level hierarchy has been supported by studies that showed similar M-modes but different multi-Mmode co-variation indices across different tasks and subjects (Krishnamoorthy et al 2003a;Danna-Dos-Santos et al 2007) and also by reports of changes in the M-mode composition in unusual conditions (Krishnamoorthy et al 2004) and with practice (Asaka et al 2007). …”

Section: Introductionmentioning

confidence: 97%

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Multi-muscle synergies in an unusual postural task: quick shear force production

2008

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We considered a hypothetical two-level hierarchy participating in the control of vertical posture. The framework of the uncontrolled manifold (UCM) hypothesis was used to explore the muscle groupings (M-modes) and multi-M-mode synergies involved in stabilization of a time profile of the shear force in the anterior-posterior direction. Standing subjects were asked to produce pulses of shear force into a target using visual feedback while trying to minimize the shift of the center of pressure (COP). Principal component analysis applied to integrated muscle activation indices identified three Mmodes. The composition of the M-modes was similar across subjects and the two directions of the shear force pulse. It differed from the composition of M-modes described in earlier studies of more natural actions associated with large COP shifts. Further, the trial-to-trial M-mode variance was partitioned into two components: one component that does not affect a particular performance variable (V UCM ), and its orthogonal component (V ORT ). We argued that there is a multi-M-mode synergy stabilizing this particular performance variable if V UCM is higher than V ORT . Overall, we found a multi-M-mode synergy stabilizing both shear force and COP coordinate. For the shear force, this synergy was strong for the backward force pulses and non significant for the forward pulses. An opposite result was found for the COP coordinate: the synergy was stronger for the forward force pulses. The study shows that M-mode composition can change in a task-specific way and that two different performance variables can be stabilized using the same set of elemental variables (Mmodes). The different dependences of the ΔV indices for the shear force and COP coordinate on the force pulse direction supports applicability of the principle of superposition (separate controllers for different performance variables) to the control of different mechanical variables in postural tasks. The M-mode composition allows a natural mechanical interpretation.

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Section: Hierarchical Control Of Posture and The Reference Configuratmentioning

confidence: 91%

Section: Composition Of Muscle Modesmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 97%

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Multi-muscle synergies in an unusual postural task: quick shear force production

2008

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“…Several recent studies have shown that the composition of M-modes may change depending on the task and also at different times before and after a postural perturbation (Asaka et al 2008;Krishnamoorthy et al 2004;. Until now, there have been no attempts to compare synergy indexes computed for the same data set based on different sets of M-modes.…”

mentioning

confidence: 99%

Two aspects of feedforward postural control: anticipatory postural adjustments and anticipatory synergy adjustments

Klous

Mikulić

Latash

2011

Journal of Neurophysiology

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Klous M, Mikulic P, Latash ML. Two aspects of feedforward postural control: anticipatory postural adjustments and anticipatory synergy adjustments. J Neurophysiol 105: 2275-2288, 2011. First published March 9, 2011 doi:10.1152/jn.00665.2010.-We used the framework of the uncontrolled manifold hypothesis to explore the relations between anticipatory synergy adjustments (ASAs) and anticipatory postural adjustments (APAs) during feedforward control of vertical posture. ASAs represent a drop in the index of a multimusclemode synergy stabilizing the coordinate of the center of pressure in preparation to an action. ASAs reflect early changes of an index of covariation among variables reflecting muscle activation, whereas APAs reflect early changes in muscle activation levels averaged across trials. The assumed purpose of ASAs is to modify stability of performance variables, whereas the purpose of APAs is to change magnitudes of those variables. We hypothesized that ASAs would be seen before APAs and that this finding would be consistent with regard to the muscle-mode composition defined on the basis of different tasks and phases of action. Subjects performed a voluntary body sway task and a quick, bilateral shoulder flexion task under self-paced and reaction time conditions. Surface muscle activity of 12 leg and trunk muscles was analyzed to identify sets of 4 muscle modes for each task and for different phases within the shoulder flexion task. Variance components in the muscle-mode space and indexes of multimuscle-mode synergy stabilizing shift of the center of pressure were computed. ASAs were seen ϳ100 -150 ms prior to the task initiation, before APAs. The results were consistent with respect to different sets of muscle modes defined over the two tasks and different shoulder flexion phases. We conclude that the preparation for a self-triggered postural perturbation is associated with two types of anticipatory adjustments, ASAs and APAs. They reflect different feedforward processes within the hypothetical hierarchical control scheme, resulting in changes in patterns of covariation of elemental variables and in their patterns averaged across trials, respectively. The results show that synergies quantified using dissimilar sets of muscle modes show similar feedforward changes in preparation to action. uncontrolled manifold hypothesis DURING STANDING, the human body is inherently unstable because of the small support area, high center of mass, and multijoint design. Voluntary movements performed by a standing person contribute to problems of postural control by producing postural perturbations because of the mechanical coupling of the body segments. When a standing person performs a fast arm movement, changes in the activation of postural muscles are typically seen about 100 ms before movement initiation; these changes have been addressed as anticipatory postural adjustments (APAs; reviewed in Massion 1992). The role of APAs has been assumed to produce joint torques and forces that minimize perturbation of the vertical...

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“…Na prática clínica da Fisioterapia, é comum o treino de equilíbrio com pacientes em pé sobre superfícies estáveis e instáveis (colchonetes e espumas) 13 , ao mesmo tempo em que esses pacientes recebem um distúrbio postural externo, como, por exemplo, pegar uma bola arremessada pelo terapeuta 13 . Porém, como mencionado, APAs e APCs podem ser modificados de acordo com a característica das tarefas e da condição de estabilidade postural [7][8][9][10][11][12] . Desta forma, as estratégias de ajuste postural sob esse tipo de intervenção fisioterapêutica merecem investigação adicional.…”

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Ajustes posturais antecipatórios e compensatórios ao pegar uma bola em condição de estabilidade e instabilidade postural

et al. 2012

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RESUMO | Indivíduos jovens pré-selecionam suas estratégias de ajuste postural antes que uma perturbação externa ocorra, com base nas características da tarefa. Entretanto, ainda não é bem conhecido de que maneira o sistema nervoso central lida com os ajustes posturais antecipatórios e compensatórios, mediante alguns treinos de equilíbrio que são comumente usados na prática clí-nica da Fisioterapia. Treze adultos jovens receberam 20 perturbações posturais externas de pegar uma bola arremessada pelo experimentador sobre condições de estabilidade e instabilidade postural (sobre uma espuma). As atividades eletromiográficas dos músculos tríceps braquial (músculo focal), retoabdominal e paravertebral lombar foram avaliadas nas janelas de tempo típicas dos ajustes posturais antecipatórios e compensatórios, assim como o pico do deslocamento do centro de pressão corporal após a perturbação. A magnitude das integrais da atividade eletromiográfica do músculo tríceps braquial foi significativamente menor em condição de instabilidade postural, não houve diferença estatística entre as condições para as integrais da atividade eletromiográfica dos músculos retoabdominal e paravertebral lombar. O pico do deslocamento anteroposterior do centro de pressão corporal foi similar entre as duas condições. Treino de equilíbrio associado à perturbação externa da postura sobre espuma pode não ser mais eficaz ou eficiente do que sobre uma superfície estável, quando se pretende alterar a atividade dos músculos posturais do tronco. Além disso, este tipo de ABSTRACT | Young individuals preselect their postural adjustment strategies before an external perturbation, based on the characteristics of the task. However, it is not well documented how the central nervous system deals with anticipatory and compensatory postural adjustments during some balance training programs, which are commonly used in Physical Therapy settings. Thirteen young individuals were submitted to 20 external postural perturbations of catching a ball thrown by an experimenter in conditions of postural stability and instability (standing on a foam). The electromyographic activities of triceps brachii (focal muscle), rectus abdominis, and lumbar paraspinal muscles were investigated in the time windows typical for anticipatory and compensatory postural adjustments, as well as the center of body pressure peak displacement after the perturbation. The magnitude of the triceps brachii integral electromyographic activity was significantly smaller in conditions of postural instability, there was no statistical difference between the stable and unstable conditions for the integral electromyographic activity of the rectus abdominis, and lumbar paraspinal muscles. The peak of the center of body pressure anterior posterior displacement was similar between the two conditions. Balance training associated with external perturbation standing on a foam might not be more effective or efficient than when standing on a stable surface, when it seeks to modify the activity of the postural trunk m...

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Learning effects on muscle modes and multi-mode postural synergies

Cited by 72 publications

References 41 publications

Multi-muscle synergies in an unusual postural task: quick shear force production

Multi-muscle synergies in an unusual postural task: quick shear force production

Two aspects of feedforward postural control: anticipatory postural adjustments and anticipatory synergy adjustments

Ajustes posturais antecipatórios e compensatórios ao pegar uma bola em condição de estabilidade e instabilidade postural

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