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

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.