Test-retest reliability of an iPhone application and measurement protocol to investigate trunk proprioception

Abstract

Several application developers have offered an application on iPhone for the physical therapist to measure range of motion. This application can be used to investigate lumbar proprioception in patients with low back pain. However, this iPhone application and measurement protocol should be tested for test-retest reliability prior to clinical usage. Therefore, the purpose of the study was to determine test-retest reliability of an iPhone application and measurement protocol. Thirty healthy subjects (mean age20.4±1.4 years; 93% female; BMI 21.0±2.7 kg/m²) were recruited into this present study. Two iPhones were attached at lumbar spine (L1) and sacrum (S2) by Velcro straps. Each subject performed 2 sets of 3 repetitions of active forward trunk bending (Test). Angle from each iPhone was recorded. The angle difference between the two iPhones represented lumbar range of motion. Mean across 3 repetitions was calculated for each set. After completion of 2 sets of forward bend, subjects rested for 15 minutes, and all iPhones were detached from the subjects. After 15 minute rest, subjects underwent the same testing protocol again (Retest). Mean of set 1 and 2 were used to determine test-retest reliability of an iPhone application, while mean of test and retest were used to determine test-retest reliability of our protocol. Intraclass correlation coefficient (ICC) and Minimal detectable change (MDC) were used for statistical analysis. The results demonstrated ICC_3,k of an iPhone application was 0.95 with MDC equaled to 4.77^๐, and ICC_2,k of  our protocol was 0.67 with MDC equaled to 12.27^๐. Based upon our results, it could be concluded that an iPhone application and our measurement protocol have adequate test-retest reliability, and can be clinically used to further investigate lumbar proprioception in patients with low back pain.