The effects of forearm support and shoulder posture on upper trapezius and anterior deltoid activity.
Josiane Sotrate Gonçalves, Cristiane Shinohara Moriguchi, Karina Sachiko Takekawa and 2 others
PMID 28603347WHAT IT FOUND
Resting the forearm on a table lowered upper trapezius and anterior deltoid muscle work at all shoulder flexion angles in asymptomatic women.
Without support, raising the arm progressively increased muscle work.
Key findings
01Forearm support reduced upper trapezius and anterior deltoid activity at all tested shoulder flexion angles; mean reductions were 3.8% MVIC for upper trapezius and 7.8% MVIC for anterior deltoid.
02Without forearm support, increasing arm elevation raised anterior deltoid activity by 11.9% MVIC and upper trapezius activity by 3.2% MVIC.
03With forearm support, upper trapezius activation was highest at 15°, and 0° was higher than 45° and 60°; without support, activation rose progressively with arm flexion.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study was small and included only asymptomatic female right-handed university students, so it does not show what happens in men, people with symptoms, or other groups. The sample size was not sufficient to detect three-way interactions. Each posture was held for only 30 seconds, and muscle fatigue was not evaluated, so it may not reflect longer work periods. The outcomes were muscle activity and weight bearing, not pain, function, or musculoskeletal disorders.
The easy way to misread this
Do not conclude that forearm support prevents neck or shoulder pain. The study measured brief upper trapezius and anterior deltoid activity in asymptomatic women, not symptoms or long-term outcomes.