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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

Results of the EMG measurements normalized to MVC. Mean and standard deviations over all subjects are shown. The panels present FT, RT and PT from left to right. Inside each window from left to right, the three bandwidths, 0.7, 1.2 and 2.0 Hz are presented
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Fig4: Results of the EMG measurements normalized to MVC. Mean and standard deviations over all subjects are shown. The panels present FT, RT and PT from left to right. Inside each window from left to right, the three bandwidths, 0.7, 1.2 and 2.0 Hz are presented

Mentions: Figure 4 shows the mean EMG level for all conditions. During PTs significantly (p < 0.01) more EMG activity was found compared to FTs and RTs, indicating increased muscle co-contraction. FTs entail a slight, but significant (p < 0.01), increase in EMG with respect to RTs. Within the tasks no significant effect of bandwidth on the mean EMG level was found.Fig. 4


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)

Results of the EMG measurements normalized to MVC. Mean and standard deviations over all subjects are shown. The panels present FT, RT and PT from left to right. Inside each window from left to right, the three bandwidths, 0.7, 1.2 and 2.0 Hz are presented
© Copyright Policy
Related In: Results  -  Collection

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

Fig4: Results of the EMG measurements normalized to MVC. Mean and standard deviations over all subjects are shown. The panels present FT, RT and PT from left to right. Inside each window from left to right, the three bandwidths, 0.7, 1.2 and 2.0 Hz are presented
Mentions: Figure 4 shows the mean EMG level for all conditions. During PTs significantly (p < 0.01) more EMG activity was found compared to FTs and RTs, indicating increased muscle co-contraction. FTs entail a slight, but significant (p < 0.01), increase in EMG with respect to RTs. Within the tasks no significant effect of bandwidth on the mean EMG level was found.Fig. 4

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