Feedback control of upright seating with functional neuromuscular stimulation during a reaching task after spinal cord injury: a feasibility study.
Aidan R W Friederich, Xuefeng Bao, Ronald J Triolo and 1 others
PMID 36510259WHAT IT FOUND
Feedback-controlled electrical stimulation helped four of five people with spinal cord injury return to an upright seated position faster after reaching for a weighted jar.
Effects on trunk sway and reach distance varied widely between individuals, and one person with a lower-level injury saw no benefit.
Key findings
01Feedback control significantly reduced the time to return to an upright position after deploying a weighted jar for four of the five subjects.
02The controller significantly reduced postural sway for only two subjects and significantly increased mean effective reach for three, while decreasing it for one and showing no effect for another.
03The subject with the lowest level of injury (T10) showed no statistically significant improvement in any outcome measure, likely because he retained more voluntary trunk control.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study included only five participants, so the results cannot be generalized to the broader spinal cord injury population. Participants used compensatory strategies, such as pressing their non-active hand against their abdomen or pushing down on the jar, which likely influenced the outcomes and make it unclear how much of the stability was due to the controller versus these self-generated bracing actions. The controller did not address trunk rotation, and the linear control algorithm may have been exceeded during large trunk movements, which could explain why benefits were less evident for reaches to the furthest station. The subject with the lowest level of injury (T10) showed no benefit, suggesting the system may only be useful for individuals with higher-level injuries and less voluntary trunk control. This was a single-session laboratory study, and the effects of fatigue and the practicality of the system in a home environment have not been established.
Declared interests
The research was supported by the National Institutes of Health and the U.S. Department of Defense. The authors did not declare any financial conflicts of interest.
The easy way to misread this
Do not interpret the faster return to upright as proof that this specific stimulation system works for all people with spinal cord injury. The benefit was inconsistent across the five participants, and the one with the lowest-level injury saw no effect at all. Furthermore, the participants were allowed to brace themselves with their hands and arms, so it is impossible to separate the effect of the electrical stimulation from these compensatory strategies.