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Updated: Jul 3, 2026
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Frame-by-Frame Video Analysis of Idiosyncratic Reach-to-Grasp Movements in Humans
Published on: January 15, 2018
Resolving kinematic redundancy in target-reaching movements with and without external constraint
Dongpyo Lee1, Daniel M Corcos, Jonathan Shemmell
1Department of Kinesiology and Nutrition, University of Illinois, Mail Code 517, 1919 W. Taylor Street, Chicago, IL 60612, USA.
Experimental Brain Research
|July 30, 2008
Summary
Human movement coordination relies on a few key couplings of body segment motions, not mechanics. These movement rules remain consistent even when knee joints are restricted, suggesting neural control.
Area of Science:
- Biomechanics
- Motor Control
- Human Movement Analysis
Background:
- Target-reaching movements involve complex coordination of multiple body segments.
- Understanding how the nervous system controls redundant degrees of freedom (DoFs) in human motion is crucial.
Purpose of the Study:
- To identify rules governing motion apportionment among body segments during reaching tasks.
- To investigate if these rules change when knee joint motion is restricted.
Main Methods:
- Principal component analysis (PCA) was used to analyze segment orientations during reaching movements.
- Participants performed reaching tasks with and without knee joint bracing.
- Effective degrees of freedom (DoFs) were extracted to describe segment couplings.
Main Results:
- Two effective DoFs explained segment excursions in unrestricted movements.
- Distinct sets of two effective DoFs characterized knee-flexing and non-knee-flexing groups.
- A small number of DoFs (2-3) accounted for altered movements with knee restriction.
Conclusions:
- Kinematic redundancy in reaching movements is resolved by a limited number of segment motion couplings.
- The robustness of these couplings against mechanical restriction suggests a neural origin.
- These findings offer insights into the neural control of goal-directed movements.
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