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Altered phalanx force direction during power grip following stroke.
1Department of Industrial and Manufacturing Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI, 53211, US.
Experimental Brain Research
|March 22, 2015
Summary
Stroke survivors exhibit altered power grip biomechanics, with greater phalanx force angular deviation increasing object dropping risk. This deviation also contributes to reduced grip strength post-stroke.
Area of Science:
- Biomechanics
- Neurorehabilitation
- Human Motor Control
Background:
- Severe stroke survivors often rely on power grip due to impaired fine motor skills.
- Limited understanding exists regarding altered power grip mechanics beyond reduced strength.
Purpose of the Study:
- To characterize static power grip in stroke survivors, focusing on phalanx force angular deviation.
- To compare grip biomechanics, muscle activity, and friction in stroke survivors versus controls.
Main Methods:
- Compared static power grip at 100% and 50% maximum grip in 11 stroke survivors and 11 controls.
- Measured phalanx force angular deviation and its contribution to total normal force.
- Assessed muscle activity and skin coefficient of friction in separate groups of stroke survivors and controls.
Main Results:
- Stroke survivors showed a 34% greater phalanx force angular deviation (19° ± 2°) compared to controls (14° ± 1°).
- This deviation approached the slippage threshold, potentially explaining object dropping.
- Altered force direction reduced normal grip force, contributing to decreased grip strength.
Conclusions:
- Increased phalanx force angular deviation is a key biomechanical alteration in stroke survivors' power grip.
- This deviation, possibly linked to muscle underactivation or sensory deficits, impacts grip function and strength.
- While overall strength is reduced, force distribution across the hand remains similar.
