The effects of passive stiffness compensation, by negative stiffness, on active RoM and controllability of the ankle joint

Introduction: Paresis in UMND patients leads to immobilization and disuse of the ankle joint. As a result, secondary changes such as increased passive stiffness and plastic CNS rearrangements aggravate the paresis. We propose an intervention that compensates the passive stiffness, enabling the remaining muscle force to initialize movement to prevent immobilization and disuse and to maximize controllability. Passive stiffness compensation is achieved by applying negative stiffness. The research question is: Does negative stiffness increase active RoM and how does this effect controllability of the ankle joint. Methods: By applying, subject speci?c, negative sti?ness on an electrical joint manipulator the change on active RoM and controllability of the ankle joint by di?erent levels of stiffness compensation is assessed. Ten healthy and two UMND patients participated in this study. Results: Active dorsi?exion RoM increased with 27.81% with the largest negative stiffness (50%) compensation (p=0.001) compared to the RoM in normal (0%) compensation. Muscle activation did not differ between the conditions. Jerk of the ankle was 59.51% (p<0.001) of the normal (0%) compensation condition with 50% negative stiffness. Conclusion: Negative stiffness compensation enabled the subjects to achieve a larger dorsi?exion RoM using the same voluntary muscle activation. To evaluate the effects of negative stiffness in walking additional experiments are needed.

Subject

negative stiffness

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http://resolver.tudelft.nl/uuid:34d451a2-f629-4df8-b6d8-cc7a8e9009e3

Embargo date

2018-01-14

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Student theses

Document type

master thesis

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Thesis_Leon_Derks.pdf

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