Fixed muscle synergies and their potential to improve the intuitive control of myoelectric assistive technology for upper extremities.
Tim A Valk, Leonora J Mouton, Egbert Otten and 1 others
PMID 30616663WHAT IT FOUND
In 11 able-bodied people, 3-5 muscle patterns explained finger and rod movements, but patterns changed with rod length.
A pooled set of 6-8 helped across lengths. The paper proposes this for device control, but it was not tested in patients.
Key findings
01In 11 healthy participants, 3-5 muscle patterns explained 73.8-81.1% of the recorded muscle signals for each finger or rod.
02A pooled set of 6-8 muscle patterns explained signals across all end-effectors as well as the separate sets.
03The muscle patterns changed with end-effector length, and only half of the participants had one or two patterns shared across all end-effectors.
STILL TO COME
How it was doneWhat they foundWhat it means for OTs
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What it does not show
Eleven healthy young adults were tested, so the findings do not show what happens in patients with neuromotor deficits. No actual myoelectric assistive device was tested, so this does not show that such a device would work better. The task was only pointing with the finger or rods, not everyday grasping or device use. Muscle patterns may have changed because of the rods' biomechanical and task demands, not because fixed spinal networks were selected. Joint-angle results were missing for two participants because landmarks could not be digitized. The authors note the sample was small, though effects were systematic across participants.
The easy way to misread this
Do not conclude that myoelectric assistive technology should be controlled by muscle synergies. The study tested healthy adults moving rods, not patients or devices, and the synergy patterns changed with end-effector length.