Influence Of Standing Versus Prone Posture On Strength And Stabilizing Activation During The Athletic Shoulder Test

The Athletic Shoulder (ASH) test is a well-established tool for assessing long-lever anterior shoulder strength in athletic populations to monitor strength imbalances, fatigue, and screen for injuries. A Standing ASH (STASH) test may be more ecologically valid for assessing full kinetic chain function under postural and joint stabilization demands not captured in the prone position. PURPOSE: To evaluate inter-test agreement and neuromuscular activation differences between the ASH and STASH tests to understand how different stabilization demands impact test performance. METHODS: Forty-two active adults (19M, 23F; 22 ± 2.5 years) performed two maximal repetitions of each abduction position (T=90°, Y=135°, I=~180°) of the ASH and STASH tests with each arm against a floor- or wall-mounted force plate, respectively. Surface electromyography (sEMG) electrodes were placed on the pectoralis major, anterior and posterior deltoid, superior and inferior trapezius, and infraspinatus. Body weight normalized peak force measurements and normalized sEMG peak amplitudes were quantified from each trial. Absolute agreement and proportional biases for force outputs were established using Bland-Altman analysis. sEMG results compared STASH to ASH activation using Wilcoxon signed rank tests with Bonferroni correction. RESULTS: Bland-Altman analyses demonstrated significant bias with greater force output during the ASH test than STASH (T=44.86%, Y=52.2%, I=62.7%; all p