Abstract
An investigation was undertaken to determine whether ankle stretch reflexes vary with the task performed by a subject. We measured reflex gain in three subjects while they performed position-matching and torque-matching tasks. In the position-matching task, subjects were required to hold their foot at a desired position while a hydraulic actuator, configured to act like a compliant spring, applied random torque perturbations to their ankle. In the torque-matching task, subjects were required to maintain a desired torque while their foot position was perturbed randomly by the actuator which behaved as a very stiff position control servo. Care was taken to ensure that the movements resulting from the perturbations were similar in both tasks. A nonlinear identification procedure was used to identify the reflex and intrinsic stiffness. Reflex stiffness was greater in the position-matching task than in the torque-matching task in all three subjects. In contrast, intrinsic stiffness was task-independent. Thus, subjects appeared to modulate their reflexes in a way appropriate to the task, supporting the hypothesis that the nervous system has the ability to modulate the stretch reflex characteristics to meet the needs of the task.
Original language | English (US) |
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Pages (from-to) | 1487-1490 |
Number of pages | 4 |
Journal | Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings |
Volume | 2 |
State | Published - 2003 |
Event | A New Beginning for Human Health: Proceddings of the 25th Annual International Conference of the IEEE Engineering in Medicine and Biology Society - Cancun, Mexico Duration: Sep 17 2003 → Sep 21 2003 |
Keywords
- Ankle stiffness
- Impedance control
- Intrinsic
- Stretch reflex
- Task
- Torque
ASJC Scopus subject areas
- Signal Processing
- Biomedical Engineering
- Computer Vision and Pattern Recognition
- Health Informatics