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A rigorous model of reflex function indicates that position and force feedback are flexibly tuned to position and force tasks.

Mugge W, Abbink DA, Schouten AC, Dewald JP, van der Helm FC - Exp Brain Res (2009)

Bottom Line: This study aims to quantify the separate contributions of muscle force feedback, muscle spindle activity and co-contraction to the performance of voluntary tasks ("reduce the influence of perturbations on maintained force or position").Inhibitory, as well as excitatory force feedback, was needed to account for the full range of measured experimental behaviors.In conclusion, force feedback plays an important role in the studied motion control tasks (excitatory during position tasks and inhibitory during force tasks), implying that spindle-mediated feedback is not the only significant adaptive system that contributes to the maintenance of posture or force.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Neuromuscular Control, Department of Biomechanical Engineering, Mechanical Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands. w.mugge@tudelft.nl

ABSTRACT
This study aims to quantify the separate contributions of muscle force feedback, muscle spindle activity and co-contraction to the performance of voluntary tasks ("reduce the influence of perturbations on maintained force or position"). Most human motion control studies either isolate only one contributor, or assume that relevant reflexive feedback pathways during voluntary disturbance rejection tasks originate mainly from the muscle spindle. Human ankle-control experiments were performed, using three task instructions and three perturbation characteristics to evoke a wide range of responses to force perturbations. During position tasks, subjects (n = 10) resisted the perturbations, becoming more stiff than when being relaxed (i.e., the relax task). During force tasks, subjects were instructed to minimize force changes and actively gave way to imposed forces, thus becoming more compliant than during relax tasks. Subsequently, linear physiological models were fitted to the experimental data. Inhibitory, as well as excitatory force feedback, was needed to account for the full range of measured experimental behaviors. In conclusion, force feedback plays an important role in the studied motion control tasks (excitatory during position tasks and inhibitory during force tasks), implying that spindle-mediated feedback is not the only significant adaptive system that contributes to the maintenance of posture or force.

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Related in: MedlinePlus

Frequency domain validation of the parametric fit for a typical subject. Magnitude and phase of the parameterized model (solid line) are shown on top of the frequency response function from the ARMAX-approximated signals (averaged over four repetitions, represented by a dotted line). As a reference, the spectral frequency response function estimated from the measured signals (averaged over four repetitions) is shown by the dashed line. The admittances in response to a 0.7 Hz perturbation bandwidth are presented for FT (left), RT (middle) and PT (right)
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Fig8: Frequency domain validation of the parametric fit for a typical subject. Magnitude and phase of the parameterized model (solid line) are shown on top of the frequency response function from the ARMAX-approximated signals (averaged over four repetitions, represented by a dotted line). As a reference, the spectral frequency response function estimated from the measured signals (averaged over four repetitions) is shown by the dashed line. The admittances in response to a 0.7 Hz perturbation bandwidth are presented for FT (left), RT (middle) and PT (right)

Mentions: The fit procedure yielded a parameterized model that accurately captures the dynamics: Fig. 8 shows the magnitude and phase of the admittances during FT, RT and PT as estimated with the parameter fit (solid line), with the ARMAX-approximated signals (dashed line) and with the measured signals (dotted line).Fig. 8


A rigorous model of reflex function indicates that position and force feedback are flexibly tuned to position and force tasks.

Mugge W, Abbink DA, Schouten AC, Dewald JP, van der Helm FC - Exp Brain Res (2009)

Frequency domain validation of the parametric fit for a typical subject. Magnitude and phase of the parameterized model (solid line) are shown on top of the frequency response function from the ARMAX-approximated signals (averaged over four repetitions, represented by a dotted line). As a reference, the spectral frequency response function estimated from the measured signals (averaged over four repetitions) is shown by the dashed line. The admittances in response to a 0.7 Hz perturbation bandwidth are presented for FT (left), RT (middle) and PT (right)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2821582&req=5

Fig8: Frequency domain validation of the parametric fit for a typical subject. Magnitude and phase of the parameterized model (solid line) are shown on top of the frequency response function from the ARMAX-approximated signals (averaged over four repetitions, represented by a dotted line). As a reference, the spectral frequency response function estimated from the measured signals (averaged over four repetitions) is shown by the dashed line. The admittances in response to a 0.7 Hz perturbation bandwidth are presented for FT (left), RT (middle) and PT (right)
Mentions: The fit procedure yielded a parameterized model that accurately captures the dynamics: Fig. 8 shows the magnitude and phase of the admittances during FT, RT and PT as estimated with the parameter fit (solid line), with the ARMAX-approximated signals (dashed line) and with the measured signals (dotted line).Fig. 8

Bottom Line: This study aims to quantify the separate contributions of muscle force feedback, muscle spindle activity and co-contraction to the performance of voluntary tasks ("reduce the influence of perturbations on maintained force or position").Inhibitory, as well as excitatory force feedback, was needed to account for the full range of measured experimental behaviors.In conclusion, force feedback plays an important role in the studied motion control tasks (excitatory during position tasks and inhibitory during force tasks), implying that spindle-mediated feedback is not the only significant adaptive system that contributes to the maintenance of posture or force.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Neuromuscular Control, Department of Biomechanical Engineering, Mechanical Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands. w.mugge@tudelft.nl

ABSTRACT
This study aims to quantify the separate contributions of muscle force feedback, muscle spindle activity and co-contraction to the performance of voluntary tasks ("reduce the influence of perturbations on maintained force or position"). Most human motion control studies either isolate only one contributor, or assume that relevant reflexive feedback pathways during voluntary disturbance rejection tasks originate mainly from the muscle spindle. Human ankle-control experiments were performed, using three task instructions and three perturbation characteristics to evoke a wide range of responses to force perturbations. During position tasks, subjects (n = 10) resisted the perturbations, becoming more stiff than when being relaxed (i.e., the relax task). During force tasks, subjects were instructed to minimize force changes and actively gave way to imposed forces, thus becoming more compliant than during relax tasks. Subsequently, linear physiological models were fitted to the experimental data. Inhibitory, as well as excitatory force feedback, was needed to account for the full range of measured experimental behaviors. In conclusion, force feedback plays an important role in the studied motion control tasks (excitatory during position tasks and inhibitory during force tasks), implying that spindle-mediated feedback is not the only significant adaptive system that contributes to the maintenance of posture or force.

Show MeSH
Related in: MedlinePlus