An electromyographic and kinematic study of the scapular stabilisers.
Sonia Briel, Benita Olivier, Witness Mudzi
PMID 33102885WHAT IT FOUND
In healthy shoulders, lower serratus anterior activity was higher than lower trapezius activity during frontal abduction.
The two muscles were linked only early in abduction.
Key findings
01The only significant increase in the mean EMG ratio of serratus anterior lower fibres versus lower trapezius in sagittal flexion versus frontal abduction was at 60% of frontal abduction (p = 0.03).
02For abduction, there was a strong negative correlation between serratus anterior lower fibres and lower trapezius EMG activity at the start (p = 0.01; r = −0.623) and at 10% (p = 0.004; r = −0.675).
03No correlation existed between the two muscles in flexion at the start (p > 0.05; r = −0.061) or at 10% (p > 0.05; r = −0.211), and poor correlation existed for the remainder of both flexion and abduction.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study used a convenience sample of 16 asymptomatic adults aged 18 to 35 years, so it may not represent the general population. All participants were right-handed and only the right arm was used for kinematic data collection, so the findings may not apply to other arms or handedness. The participants had healthy shoulders and no pain or surgery, so the results cannot be treated as evidence about painful or pathological shoulders. The paper reports EMG and kinematic measurements, not a treatment trial or patient outcome, so it cannot show that strengthening either muscle improves shoulder function. The sample was described as small because EMG and kinematic collection is complex.
The easy way to misread this
Do not read the higher serratus anterior activity as proof that strengthening it treats painful shoulders. The study measured only healthy adults and did not test patients or treatment outcomes.