Intra- and Inter-Rater Reliability of a Clinical Test for Scapular Dyskinesis in Beach Tennis Athletes

Abstract

Introduction. Given the potential influence of biomechanical demands imposed by beach tennis (BT) on athletes’ scapular movement patterns, it is essential to ascertain the reliability of clinical tests for scapular dyskinesis (SD) in this particular population. Objective. To investigate the intra- and inter-rater reliability of a clinical test for SD in BT athletes. Method. Two blinded raters (a novice and an expert) independently evaluated SD in 58 BT athletes using the same video recordings to determine inter‑rater reliability. Furthermore, intra-rater reliability was assessed by examining the consistency of SD classifications made by the novice rater across two trials. Each scapula was independently classified as normal, subtle, or obvious dyskinesis. The intra- and inter-rater reliability was determined by use of linear weighted Kappa (κw). Results. For the dominant extremity, the expert rater classified approximately 32.5% [95%CI: 17.3 to 55.6] of right-handed athletes and 16.7% [95%CI: 3.4 to 48.7] of left-handed athletes as presenting SD. The novice rater identified approximately 25.0% [95%CI: 12.0 to 46.0] of right-handed athletes and 22.2% [95%CI: 6.1 to 56.9] of left-handed athletes with SD. Inter-rater reliability was low for the left upper extremity (κw = 0.132 [95%CI: −0.15 to 0.42]) and moderate for the right upper extremity (κw = 0.601 [95%CI: 0.39 to 0.81]). Intra-rater reliability demonstrated substantial agreement for both the left (κw= 0.594 [95%CI: 0.33 to 0.86]) and right (κw = 0.693 [95%CI: 0.51 to 0.88]) upper extremity. Conclusion. The clinical test for SD demonstrated substantial intra-rater reliability, but variable inter-rater reliability among BT athletes.