RESUMEN
Objective: To investigate the reliability and validity of an iPhone® application (iHandy® Level) for measuring active lumbar flexion-extension range of motion (ROM) in chronic nonspecific low back pain (CNLBP) patients. Methods: Fifteen CNLBP patients were recruited. The participants stood in a relaxed position and the T12-L1 and S1-S2 spinal levels were identified through palpation and were marked on the skin. Two blinded examiners used a gravity-based inclinometer and the application in order to measure ROM. The instruments were lined up appropriately and the participants were asked to perform maximum lumbar flexion following by maximum extension. First, each examiner placed the instruments over the T12-L1 level and then over the S1-S2 level during the movements. In order to calculate flexion-extension ROM, the measurement which was obtained from T12-L1 was subtracted from S1-S2. Intraclass correlation coefficient (ICC) models (3, k) and (2, k) were used in order to determine the intrarater and inter-rater reliability, respectively. The Spearman's correlation coefficients (rs ) and Bland-Altman plots were used in order to examine the validity. Results: Fair-to-excellent intrarater (ICC = 0.39-0.89) and moderate-to-good inter-rater reliability (ICC = 0.55-0.77) were observed using the inclinometer. Moreover, poor-to-good intrarater (ICC = 0.30-70) and inter-rater (ICC = 0.13-0.70) reliability were found with the application. The Spearman's correlation coefficients demonstrated low-to-moderate associations between the measures of the two instruments (rs ≥ 0.22). The Bland-Altman plots indicated that there was a significant difference between the instruments for measuring flexion ROM. The difference was not significant for measuring extension ROM. Conclusion: The iHandy® Level application does not have sufficient validity for measuring active lumbar flexion ROM in CNLBP patients.