Repeatability of electromyography recordings and muscle synergies during gait among children with cerebral palsy.
Katherine M Steele, Meghan E Munger, Keshia M Peters and 2 others
PMID 30396059WHAT IT FOUND
Muscle activity and groups of muscles activated together during gait were repeatable across two visits in 20 children with bilateral cerebral palsy.
Step-to-step variation was still common, so very small changes between visits should not be treated as real movement changes.
Key findings
01Surface EMG waveforms were highly similar within a visit and across visits.
02For six participants, the number of synergies needed to explain EMG activity changed between visits, but the absolute change in total variance accounted for was not different from participants whose synergy number did not change.
03Children with CP needed an average of 3.1 synergies to describe over 95% of EMG variance, with a range of 2 to 4.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only 20 children with bilateral cerebral palsy who walked independently without walkers or crutches were studied, so the results may not apply to children with unilateral cerebral palsy or assisted walking. One participant was excluded from the synergy analyses because gastrocnemius EMG data were missing at the first visit. The visits were allowed to be up to six weeks apart, and walking speed was not controlled, so normal variation in walking speed between visits is included in the repeatability estimate. EMG magnitude was normalised to the peak value at each visit, which may hide true changes in muscle activity after interventions such as surgery or botulinum toxin injections.
Declared interests
The authors declared no conflicts of interest. The article is listed as supported by NIH extramural research support and non-U.S. government research support.
The easy way to misread this
Do not conclude that a small change in EMG waveform or synergy number between visits shows that a treatment changed a child's movement. Six participants changed synergy number between visits, but their absolute change in total variance accounted for was not different from participants whose synergy number did not change.