Assessment of Intra-Day and Inter-Day Reliability of Novel Measures of Shoulder Neuromuscular Control

Abstract

0839 The external validity of shoulder neuromuscular control measures has been limited by the predominance of proprietary, custom-made laboratory devices that have not permitted direct comparisons across research settings. The reliability of a new, commercially-available, computerized testing system that measures critical tracking tasks (CTT) that involve visual perception and neuromuscular control of the shoulder has not yet been established. PURPOSE: To determine the intra-day and inter-day reliability of measures of shoulder neuromuscular control using CTT presented by a new, commercially-available system. METHODS: Twenty healthy subjects (10 women, 10 men; mean age, 24.1 + 5.7 yrs) with no history of visual or vestibular disability, or upper limb impairment participated in this study. The computerized CTT required the subjects to perform rapid, subtle shoulder internal and external rotation movements in the scapular plane in attempt to continuously correct the changing position of an object on a computer screen. Test-retest reliability for 2 of 3 levels of CTT difficulty (Intermediate and Advanced) was calculated in this study. Each subject completed her/his retest within 24 hours of the initial test. Intraclass correlation coefficients (ICC) were calculated for intra-day and inter-day results using repeated measures ANOVAs for the system's two outcome measures, Coordination and Concentration. Level 2 reliability was calculated from the results of one set of 5 repetitions, while Level 3 reliability was determined from the average of 3 sets of 5 repetitions. RESULTS: The reliability betweens sets on Day 1 at Level 3 (Advanced) ranged from moderate (ICC = .707) to poor (ICC = .294). The reliability between trials at Level 3 improved on Day 2, and was classified as high (ICC = .800 to .818). Testretest (inter-day) reliability at Level 2 (Intermediate) ranged from moderate (ICC = .521) to poor (ICC = .143) for dominant and non-dominant limbs. On Day 2 at Level 3 (Advanced), subjects demonstrated moderate (ICC = .700) to poor (ICC = .408) test-retest reliability. CONCLUSION: The system's critical tracking tasks are novel motor activities that require at least 2 days of practice to minimize learning effects, as mean scores improved significantly from Day 1 to Day 2 (p < 0.05). Our findings do not support the continued use of the Concentration variable, as its reliability is poor (ICC < .440). Based on the high test-retest reliability observed on Day 2 (ICC > .80), researchers/clinicians can be confident of the repeatability of the Coordination variable, provided the subject has been given sufficient practice. Supported by Northwest Health Foundation Grant #2002–220