Comparisons of test-retest reliability of infraspinatus strength during wiper exercise with and without external fixation in individuals of scapular dyskinesis

BackgroundThe wiper exercise in a side-lying position is commonly used in clinical settings to assess the strength of the infraspinatus muscle. In addition, a reliable test of infraspinatus strength is important for individuals with scapular dyskinesis.ObjectiveThe purpose is to compare the test-retest reliability of infraspinatus strength during the wiper exercise with and without external fixations in individuals with scapular dyskinesis.MethodsThirty individuals with scapular dyskinesis participated. A dynamometer was utilized to measure the strength of the infraspinatus during the wiper exercise with and without external fixation applied to the posterior superior iliac spine (PSIS) and spinous process of a fourth thoracic vertebra (T4). The intra-class correlation coefficients (ICC 3,1) were used to compare the reliability of infraspinatus strength measurement.ResultsThe reliability for infraspinatus strength measurement was higher with external fixation than without external fixation. The ICC value during wiper exercise with external fixation was 0.99 (95% confidence interval: 0.96-0.99; P < 0.01), and the average strength was 7.35 ± 2.2 kg. In contrast, the ICC value during wiper exercise without external fixation was 0.79 (95% confidence interval: 0.49-0.93; P < 0.01), and the average strength was 5.86 ± 1.45 kg.ConclusionIn individuals with scapular dyskinesis, the infraspinatus strength measurement during the wiper exercise with external fixation is recommended to improve the test-retest reliability.