Study Reveals Unseen Changes In Motor Control After Spinal Cord Injury
Even when people with incomplete spinal cord injuries can walk, everyday functions like standing, balancing or producing steady force may remain difficult. A new study shows why.
Using surface skin electrical sensors, a research team in Sweden identified previously unseen changes in motor coordination that result from incomplete spinal cord injuries (SCI). The study is the first to examine how individual motor units – that is, nerve-to-muscle connections that create movement – work together in people with SCI.
“Our study reveals, at the cellular level, how the central nervous system adapts to the injury to control movement,” says Ruoli Wang, associate professor in biomechanics at Promobilia MoveAbility lab, KTH Royal Institute of Technology. She says the researchers’ approach was completely non-invasive.
The results were published in the Journal of NeuroEngineering and Rehabilitation.
Adaptation of Motor Unit Synergies In The Synergetic Ankle Plantarflexors In Ambulatory Persons With Incomplete Spinal Cord Injury
The study’s lead author, PhD student Zhihao Duan, says the researchers found the nervous system struggles to spread signals smoothly across muscles at low levels of exertion after the injury. And it appears to overcompensate at higher levels of exertion, sending “louder”, less refined signals.
A single muscle moves through hundreds of motor units, each turning on and off precisely to create smooth force. Composed of a single motor neuron and its connecting muscle fibers, these motor units respond to shared signals from the nervous system, much like different sections of musicians led by an orchestra conductor. That shared input is what allows them to act in coordinated patterns.
To explore how well these units coordinate under the control of the central nervous system the team examined 25 people (including 10 control participants). They used high density electromyography (HD-EMG) to measure electrical activity in the functionally similar calf muscles – soleus and gastrocnemius – while volunteers pushed lightly or moderately against a force measurement device.
