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.
Chirosa-Ríos et al. (Thu,) studied this question.