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

Thomas, Robert; Zatsiorsky, Vladimir M.; Latash, Mark L.

doi:10.1007/s00221-008-1299-7

Cited by 53 publications

(46 citation statements)

References 40 publications

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“…There were three types of M-modes based on muscles that loaded higher than 0.50 (Robert & Latash, 2008;Krishnan et al, 2011). Visual inspections of the scree plots confirmed the validity of this criterion.…”

Section: M-modes Extractionsupporting

confidence: 54%

“…The reciprocal M-modes may effectively move the body forward or backwards, while the co-contractions M-modes may improve performance by stiffening the joints to resist perturbations. Co-contractions patterns occurred more frequently under unstable conditions Robert et al, 2008), in individuals with Down's syndrome (Aruin & Almeida, 1997) and persons with neurological disorders (Woollacott & Burtner, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Age Effects on Multi-muscle Modes during Voluntary Body Sway

Wang

Watanabe

Asaka

2015

Research in Sports Medicine

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The aim of this article was to explore age-related differences in the muscle modes (M-modes) during voluntary body sway (VS). M-modes were defined as trunk and leg muscles organized into groups with parallel scaling of muscle activation level within a group. We hypothesized that, in comparison with young performers, older adults would show changes in the compositions of M-modes stabilizing the anterior-posterior (AP) center of pressure (COP) displacement. Young (27.5 ± 7.3 yr, 164.6 ± 9.7 cm and 58.4 ± 10.6 kg) and older (69.4 ± 6.4 yr, 160.0 ± 7.0 cm and 58.9 ± 7.5 kg) subjects performed the VS task in the AP direction while trying to minimize sway in the medio-lateral direction. EMG signals of 10 postural muscles were recorded and analyzed. Principal component analysis (PCA) was used to identify three M-modes within the space of integrated indices of muscle activity. The main findings were (1) that there were no age-related differences in magnitude of the COP displacement or amount of variance explained by the principal components (m-modes), and (2) that the number of times co-contraction and mixed m-modes were used were significantly higher for older adults, and the number of times reciprocal m-modes were used were significantly higher for young adults. These observations suggest that aging is associated with a reduced ability to unite dorsal and ventral muscles of the body, which may be reflective of the CNS developing a useful strategy when faced with self-triggered perturbations.

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Section: M-modes Extractionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Age Effects on Multi-muscle Modes during Voluntary Body Sway

Wang

Watanabe

Asaka

2015

Research in Sports Medicine

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“…Muscle activations reflect deviations of the actual values of elemental variables from the corresponding RC EL . In an earlier study (Robert et al 2008), changes in muscle activations during a whole-body task were directly linked to changes in the body RC in support of this general scheme.…”

Section: Discussionmentioning

confidence: 53%

Task-specific stability in muscle activation space during unintentional movements

et al. 2014

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We used robot-generated perturbations applied during position-holding tasks to explore stability of induced unintentional movements in a multi-dimensional space of muscle activations. Healthy subjects held the handle of a robot against a constant bias force and were instructed not to interfere with hand movements produced by changes in the external force. Transient force changes were applied leading to handle displacement away from the initial position and then back towards the initial position. Inter-trial variance in the space of muscle modes (eigenvectors in the muscle activations space) was quantified within two sub-spaces, corresponding to unchanged handle coordinate and to changes in the handle coordinate. Most variance was confined to the former sub-space in each of the three phases of movement, the initial steady state, the intermediate position, and the final steady state. The same result was found when the changes in muscle activation were analyzed between the initial and final steady states. Changes in the dwell time between the perturbation force application and removal led to different final hand locations undershooting the initial position. The magnitude of the undershot scaled with the dwell time, while the structure of variance in the muscle activation space did not depend on the dwell time. We conclude that stability of the hand coordinate is ensured during both intentional and unintentional actions via similar mechanisms. Relative equifinality in the external space after transient perturbations may be associated with varying states in the redundant space of muscle activations. The results fit a hierarchical scheme for the control of voluntary movements with referent configurations and redundant mapping between the levels of the hierarchy.

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“…ΔV was transformed using Fisher's z-transformation for statistical analysis (ΔVtran) 22) . Prior to statistical analysis, we partitioned the data equally into two phases after buttocks-off (first phase and second phase).…”

Section: Data Processingmentioning

confidence: 99%

The coordination of joint movements during sit-to-stand motion in old adults: the uncontrolled manifold analysis

Anan

Hattori²,

Tanimoto

et al. 2017

Phys Ther Res

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ABSTRACT. Objective: Sit-to-stand motion (STS) is a dynamic motion utilized in fundamental activities of daily living and requires extensive joint movement in the lower extremities and the trunk and coordination of multiple body segments. The present study aimed to investigate whether aging affects the motor coordination of joint movements required to stabilize the horizontal and vertical movement of center of mass using the uncontrolled manifold (UCM) analysis. Method: We recruited 39 older adults with no musculoskeletal and/or neuromuscular conditions that affected STS, along with 21 healthy younger adults. All subjects performed five STS trials from a chair with the seat height adjusted to the length of their lower leg at a selfselected motion speed. Kinematic data were collected using a three-dimensional motion analysis system. We performed the UCM analysis to assess the effects of joint angle variance (elemental variable) to stabilize the horizontal and vertical movement of COM (performance variable) and calculated the joint angle variance that does not affect COM (VUCM), the variance that affects COM (VORT), and the synergy index (ΔV). Results: ΔV values in the horizontal direction were higher in the older adults than in the younger adults, but ΔV values in the vertical direction were lower in the older adults than in the younger adults. Conclusion: Older adults require increasing levels of stabilization of horizontal movement of COM after buttocks-off in the STS maneuver. As a result, variance in the joint angle of the lower extremities indicated no kinematic synergy for stabilizing the vertical movement of COM. Key words: Uncontrolled manifold analysis, Sit-to-stand, Aging (Phys Ther Res 20: 44-50, 2017)T he Sit-to-stand motion (STS) is a highly common motion that is performed as frequently as gait in daily life. It requires two tasks: transitioning the center of mass (COM) from a wide base of support (BOS) provided by the buttocks, thighs, and feet to a narrow BOS provided by the feet alone, and lifting the COM from the height of sitting to that of standing. STS also represents a motion for which the muscle strength of lower extremities is particularly important 1,2 ) . STS is associated with applied motions such as transfer and walking, and its acquisition is an essential factor to improve mobility capability. STS results from interactions characteristic of task-related, individual, and environmental constraints 3) . Alexander et al. 4) reported that aging affects STS acquisition, and that older adults with difficulty performing this maneuver require prolonged STS time. We reported that older subjects who experienced dif- The coordination of joint movements during STS motion 45 ficulty with this motion performed the STS using less energy and with more consideration for stability, relative to younger healthy subjects 5) . It is important to control the redundant degrees-offreedom (DOFs), which coordinate with each body segment to accomplish tasks. STS is a whole-body movement that requires simultaneous ...

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

Cited by 53 publications

References 40 publications

Age Effects on Multi-muscle Modes during Voluntary Body Sway

Age Effects on Multi-muscle Modes during Voluntary Body Sway

Task-specific stability in muscle activation space during unintentional movements

The coordination of joint movements during sit-to-stand motion in old adults: the uncontrolled manifold analysis

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