Comparison of shoulder strength assessment in scaption with an isometric dynamometer and a weighing machine: a pilot study

Abstract

BackgroundStrength testing is an important aspect of shoulder examination. To date, strength assessment has many limitations. There is no single standard instrument for measuring, and various current devices have problems in reliability, accuracy, and cost. This study compared the results of an innovative and simple method of strength testing (weighing machine) with an existing method (isometric dynamometer).MethodsShoulder strength was tested in 80 individuals, 60 with normal shoulders (group 1) and 20 with shoulder pathology (group 2). Strength was tested in the standard position of 90° of elevation in the scapular plane (scaption) with the elbow extended and forearm pronated while resistance was applied just proximal to the wrist. A weighing machine and an isometric dynamometer were used for strength testing.ResultsThere was a mean difference of 0.26 kg in group 1 (95% confidence interval [CI], 0.16-0.36; P < .0001) and 0.30 kg in group 2 (95% CI, 0,04-0,72; P = .0291) between the weighing machine and the isometric dynamometer. Although statistically significant, these differences were not clinically significant.ConclusionsThis pilot study shows that strength assessment by an innovative and simpler technique with a weighing machine gives similar results as an isometric dynamometer.