Human Postural Control: Force Plate Experiments and Modelling

Rosenblum, Michael G.; Firsov, G. I.; Kuuz, Robert; Pompe, Bernd

doi:10.1007/978-3-642-71949-3_17

Cited by 16 publications

(14 citation statements)

References 7 publications

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“…These findings suggest that failures to decouple ankle dorsi-/plantar-flexion and hip abduction/adduction may contribute to postural disruptions during dynamic stances in ASD. Increased dependency of COP AP and COP ML in ASD may reflect a reduced ability to evoke distinct motor control processes and move towards the target without generating unwanted body movements in orthogonal directions [26, 27]. …”

Section: Discussionmentioning

confidence: 99%

“…These two distinct joint movements show moderate dependency when healthy individuals attempt to remain still while standing indicating that a certain amount of shared information between ankle and hip joint movements is necessary for individuals to maintain balance. In patients with neurodegenerative disorders or when healthy participants close their eyes, a significant increase in shared information has been observed indicating an increased dependency of ankle and hip coordination when postural control systems are compromised [27] or under challenging conditions [26]. On the contrary, during self-initiated dynamic stances in which participants’ sway is targeted in one direction (i.e., either the AP or ML direction), a reduction in shared information is expected.…”

Section: Introductionmentioning

confidence: 99%

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Postural orientation and equilibrium processes associated with increased postural sway in autism spectrum disorder (ASD)

Wang

Hallac

Conroy

et al. 2016

J Neurodevelop Disord

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BackgroundIncreased postural sway has been repeatedly documented in children with autism spectrum disorder (ASD). Characterizing the control processes underlying this deficit, including postural orientation and equilibrium, may provide key insights into neurophysiological mechanisms associated with ASD. Postural orientation refers to children’s ability to actively align their trunk and head with respect to their base of support, while postural equilibrium is an active process whereby children coordinate ankle dorsi-/plantar-flexion and hip abduction/adduction movements to stabilize their upper body. Dynamic engagement of each of these control processes is important for maintaining postural stability, though neither postural orientation nor equilibrium has been studied in ASD.MethodsTwenty-two children with ASD and 21 age and performance IQ-matched typically developing (TD) controls completed three standing tests. During static stance, participants were instructed to stand as still as possible. During dynamic stances, participants swayed at a comfortable speed and magnitude in either anterior-posterior (AP) or mediolateral (ML) directions. The center of pressure (COP) standard deviation and trajectory length were examined to determine if children with ASD showed increased postural sway. Postural orientation was assessed using a novel virtual time-to-contact (VTC) approach that characterized spatiotemporal dimensions of children’s postural sway (i.e., body alignment) relative to their postural limitation boundary, defined as the maximum extent to which each child could sway in each direction. Postural equilibrium was quantified by evaluating the amount of shared or mutual information of COP time series measured along the AP and ML directions.ResultsConsistent with prior studies, children with ASD showed increased postural sway during both static and dynamic stances relative to TD children. In regard to postural orientation processes, children with ASD demonstrated reduced spatial perception of their postural limitation boundary towards target directions and reduced time to correct this error during dynamic postural sways but not during static stance. Regarding postural equilibrium, they showed a compromised ability to decouple ankle dorsi-/plantar-flexion and hip abduction/adduction processes during dynamic stances.ConclusionsThese results suggest that deficits in both postural orientation and equilibrium processes contribute to reduced postural stability in ASD. Specifically, increased postural sway in ASD appears to reflect patients’ impaired perception of their body movement relative to their own postural limitation boundary as well as a reduced ability to decouple distinct ankle and hip movements to align their body during standing. Our findings that deficits in postural orientation and equilibrium are more pronounced during dynamic compared to static stances suggests that the increased demands of everyday activities in which children must dynamically shift their COP involve more severe postural control deficit...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Postural orientation and equilibrium processes associated with increased postural sway in autism spectrum disorder (ASD)

Wang

Hallac

Conroy

et al. 2016

J Neurodevelop Disord

View full text Add to dashboard Cite

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“…However, rather than producing stereotyped rhythms as they were previously thought, they are considered nowadays to be far more flexible systems that can exploit the body dynamics instead of guiding them (cf., Bizzi and Clarac 1999;Rosenblum et al 1998;Selverston et al 2000;Rabinovich et al 2006). For instance, they can adapt their rhythms to the body's ongoing motion via proprioceptive feedback (see Grillner 2006;Levi et al 2005;Ivanenko et al 2005;Lockhart and Ting 2007) and follow multiple synergies at the same time and/or dismiss others (cf.…”

Section: Introductionmentioning

confidence: 99%

Creating and modulating rhythms by controlling the physics of the body

Pitti¹,

Niiyama

Kuniyoshi

2010

Auton Robot

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The motion behaviors of vertebrates require the correct coordination of the muscles and of the body limbs even for the most stereotyped ones like the rhythmical patterns. It means that the neural circuits have to share some part of the control with the material properties and the body morphology in order to rise any of these motor synergies. To this respect, the chemical downward neuromodulators that supervise the pattern generators in the spinal cord create the conditions to merge (or to disrupt) them by matching the phase of the neural controllers to the body dynamics. In this paper, we replicate this control based on phase synchronization to implement neuromodulators and investigate the interplay between control, morphology and material. We employ this mechanism to control three robotic setups of gradual complexity and actuated by McKibben type air muscles: a single air muscle, an elbow-like system and a leg-like articulation. We show that for specific values, the control parameters modulate the internal dynamics to match those of the body and of the material physics to either the rhythmical and non-rhythmical gait patterns.

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“…They concluded that this follows from the fact that at a certain time the postural system cannot distinguish between a random and applied perturbation, which suggests that the same neuromuscular control mechanisms are used under quiet-standing and dynamic conditions. Rosenblum et al (1998) described the behavior of the COP with two coupled chaotic oscillators. Inverted-pendulum models have also been shown to be capable of reproducing experimental sway data (Eurich and Milton 1996;Peterka 2000).…”

Section: Introductionmentioning

confidence: 99%

Stability of bipedal stance: the contribution of cocontraction and spindle feedback

Soest¹,

Haenen²,

Rozendaal³

2003

Biological Cybernetics

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Abstract. The aim of this study is to assess the contribution of cocontraction and spindle feedback to local stability during bipedal stance. To that aim, an existing nonlinear state space model of the human musculoskeletal system is linearized in a reference equilibrium state. The maximal real part of the eigenvalues of the linearized system matrix A and the low-frequency joint stiffness are used as a measure of local stability. Muscle properties, as represented in a Hill-type muscle model, are shown to improve the behavior, the improvement being larger at high cocontraction. However, even at maximal cocontraction the low-frequency joint stiffness generated by the muscle properties is insufficient to yield a locally stable system. It follows that feedback is necessary to ensure local stability. In this study, the potential contribution of spindle feedback is investigated by optimizing the feedback gains for contractile element length and velocity for each muscle. It is found that in the case of time-delayed negative feedback, it is impossible to stabilize the system on the basis of spindle feedback. When positive timedelayed feedback is allowed, a barely stable system is obtained. When the time delays are removed, the feedback gains can be chosen such that a locally stable system is obtained, indicating the limitations imposed by the presence of time delays. Finally, it is shown that for small perturbations the response of the linear system to an arbitrary perturbation is similar to that of the nonlinear system, indicating the validity of the approach used. It is concluded that the combination of muscle properties and time-delayed spindle feedback is insufficient to obtain a system with reasonable local stability.

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Human Postural Control: Force Plate Experiments and Modelling

Cited by 16 publications

References 7 publications

Postural orientation and equilibrium processes associated with increased postural sway in autism spectrum disorder (ASD)

Postural orientation and equilibrium processes associated with increased postural sway in autism spectrum disorder (ASD)

Creating and modulating rhythms by controlling the physics of the body

Stability of bipedal stance: the contribution of cocontraction and spindle feedback

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