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Passive and active lower-limb movements delay upper-limb balance reactions
S Quant1, B E Maki, M C Verrier
1Graduate Department of Rehabilitation Science, University of Toronto, 256 McCaul Street, Toronto, Ontario M5T 1W5, Canada.
Neuroreport
|October 6, 2001
Summary
Rhythmic lower-limb activity, whether active or passive, delays upper-limb balance reactions. This suggests sensory feedback from leg movement, not just active effort, influences stability control.
Area of Science:
- Neuroscience
- Biomechanics
- Human Motor Control
Background:
- Maintaining balance involves complex sensorimotor integration.
- Upper-limb reactions are crucial for stability during perturbations.
- The influence of concurrent lower-limb activity on upper-limb responses is not fully understood.
Purpose of the Study:
- To investigate how rhythmic lower-limb activity affects the timing of upper-limb balance reactions.
- To differentiate the effects of active versus passive lower-limb movement on balance control.
Main Methods:
- Healthy subjects experienced rapid sagittal chair tilts.
- Upper-limb grasping reactions were measured under three conditions: active leg pedaling, passive leg pedaling, and no lower-limb movement (control).
- Initiation and execution times of grasping reactions were analyzed.
Main Results:
- Both active and passive leg pedaling significantly delayed the initiation of grasping reactions compared to the control condition (43-47 ms delay).
- Execution of grasping reactions was also delayed by both active and passive pedaling (12-17 ms delay).
- The magnitude of delay was similar for active and passive pedaling conditions.
Conclusions:
- Sensory discharge from lower-limb movement, rather than volitional effort, is the primary factor conditioning upper-limb balance reactions.
- These findings highlight the significant role of ongoing movement, like locomotion, in modulating postural stability.
- Understanding these interactions is crucial for rehabilitation and performance enhancement in activities requiring coordinated limb movements.