Validity and Reliability of a Modified Seated Athletic Shoulder Test Using a Functional Electromechanical Dynamometer

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Abstract
Context : The athletic shoulder (ASH) test traditionally evaluates upper limb isometric strength in a prone position using a force platform. However, this position may lack functional relevance, and the force platforms are not portable. A functional electromechanical dynamometer may provide a potentially valid, reliable, portable, and standardized seated alternative. Design : Randomized, repeated-measures design to assess the between-session reliability and concurrent validity of the Modified Seated ASH Test using an electromechanical dynamometer compared with the prone ASH test using a force platform. Methods : Thirty-four active university students (15 males, 19 females; 19.73 [3.68] years) completed ASH assessments using a force platform (prone) and an electromechanical dynamometer (seated). We evaluated between-session reliability using intraclass correlation coefficients and coefficients of variation and concurrent validity using Pearson correlations ( r ) and Bland–Altman analyses. Results : The electromechanical dynamometer demonstrated excellent reliability across the 180° (I), 135° (Y), and 90° (T) positions (intraclass correlation coefficient = .91–.97, coefficients of variation = 7.25%–11.33%). The force platform also showed good to excellent reliability but with higher variability (intraclass correlation coefficient = .83–.91, coefficients of variation = 12.43%–15.89%). Electromechanical dynamometer and force platform forces correlated strongly across positions ( r = .77–.87, P < .001). However, Bland–Altman analyses revealed the electromechanical dynamometer yielded systematically higher forces (bias = 18–28 N) with nontrivial limits of agreement, indicating scores differ meaningfully between devices. Conclusions : The Modified Seated ASH test, using an electromechanical dynamometer, has good to excellent reliability for assessing upper limb isometric strength and is strongly associated with the traditional force platform-based ASH test. The presence of systematic bias and nontrivial limits of agreement indicates that electromechanical dynamometer- and force platform-derived forces should not be considered interchangeable for absolute strength quantification.

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