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Influence of Force-Length Relationship and Task-Specific Constraints on Finger Force-Generating Capacities
Benjamin Goislard de Monsabert1, Mathieu Caumes2, Eric Berton2
1Aix-Marseille University, CNRS, ISM, Marseille, France. benjamin.goislard-de-monsabert@univ-amu.fr.
Annals of Biomedical Engineering
|June 16, 2023
Summary
Wrist posture affects pinch grip strength due to the force-length relationship in finger extensors. Four-finger pressing strength, however, is not limited by muscle capacity but by finger interdependence factors.
Area of Science:
- Biomechanics
- Human Physiology
- Kinesiology
Background:
- Grip strength loss in various wrist postures is often attributed to the force-length relationship of extrinsic finger flexors.
- Emerging research suggests wrist extensor muscles also contribute to grip strength deficits.
Purpose of the Study:
- To investigate the specific role of the force-length relationship in finger force production across different wrist postures.
- To differentiate the mechanisms underlying grip strength changes in pinch grip versus four-finger pressing tasks.
Main Methods:
- 18 participants performed maximal isometric finger force tasks (pinch grip and four-finger pressing) in four wrist postures.
- Measurements included maximum finger force (MFF), joint angles, and muscle activation (electromyography).
- A musculoskeletal model estimated muscle force and length from biomechanical data.
Main Results:
- Maximum finger force (MFF) decreased in a flexed wrist posture during pinch grip.
- MFF remained consistent across different wrist postures during the four-finger pressing task.
- Pinch grip force loss in deviated wrist postures is partly linked to the force-length relationship of finger extensors.
Conclusions:
- The force-length relationship significantly impacts pinch grip strength, particularly in flexed wrist positions, due to finger extensor muscle mechanics.
- Maximum finger force during four-finger pressing appears primarily limited by mechanical and neural finger interdependence, not muscle force-length capacities.
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