Upper extremity biomechanics in native and non-native signers.
Gretchen Roman, Daniel S Peterson, Edward Ofori and 1 others
PMID 34864710WHAT IT FOUND
Native signers showed fewer micro-rests and lower muscle tension than non-natives, supporting injury risk theories.
However, natives also demonstrated greater range of motion and ballistic tendencies, contradicting the hypothesis that they have safer biomechanics.
Key findings
01Native signers had significantly more 'micro' rests and less muscle activation in the non-dominant upper trapezius compared to non-natives.
02Native signers exhibited greater wrist flexion-extension range of motion and greater anterior-posterior jerk than non-natives.
03There were no significant differences in shoulder or wrist strength between native and non-native signers.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The cross-sectional design cannot prove causation between biomechanics and injury. The sample size was small (25 participants), and the study was powered only for wrist acceleration, leaving other outcomes potentially underpowered. Fluency was assessed differently for deaf and non-deaf participants, with no standard assessment for deaf participants. One participant was excluded from rest and activation analysis due to non-physiological EMG values. Ballistic signing and joint angle were assessed using only single representative signs, not the entire signing period.
Declared interests
No specific funding or conflict of interest statements were provided in the text.
The easy way to misread this
Do not interpret the greater range of motion and ballistic tendencies in native signers as evidence of unsafe biomechanics. The study suggests these features may be characteristic of fluent, experienced signing and potentially protective, contrary to the initial hypothesis that non-natives had less favorable biomechanics.