Brief Research ReportsReproducibility of the DrGoniometer app for field-based assessment of the break-point angle in Nordic Hamstring exerciseVercelli, Stefanoa; Baldaccini, Alexb; Sartorio, Francescoa; Bravini, Elisabettac; Corna, Stefanoa; Ferriero, GiorgiodAuthor Information aPhysical and Rehabilitation Medicine Unit, Scientific Institute of Veruno, Istituti Clinici Scientifici Maugeri IRCCS, Veruno bPrivate Practice, San Pellegrino Terme cItalian Society of Physiotherapy, Firenze dPhysical and Rehabilitation Medicine Unit, Scientific Institute of Tradate, Istituti Clinici Scientifici Maugeri IRCCS, Tradate, Italy Received 25 January 2020 Accepted 21 March 2020 Correspondence to Stefano Vercelli, PhD, Physical and Rehabilitation Medicine Unit, Istituti Clinici Scientifici Maugeri, IRCCS, Via Maugeri 4, 27100 Pavia, Italy, Tel: +39 0322 884799; fax: +39 0322 884816; e-mail: email@example.com International Journal of Rehabilitation Research: September 2020 - Volume 43 - Issue 3 - p 272-275 doi: 10.1097/MRR.0000000000000415 Buy Metrics Abstract Smartphone-based measurement could represent a portable and cheap solution to assess the Nordic Hamstring break-point angle (BPA). We investigated the following: (1) the reproducibility of the DrGoniometer app, (2) its agreement with a computerized video analysis software used as a reference method, and (3) the effects of raters’ experience. Fifty recordings were processed by four independent raters. Intraclass correlation coefficient (ICC), SEM, and minimum detectable change (MDC) were calculated. Bland–Altman plots verified the limits of agreement (LoA) with the reference method. The effect of raters’ clinical experience was investigated by unpaired t-tests. The app showed excellent intra-rater (ICC = 0.89, 95% CI, 0.84–0.92) and inter-rater reliability (ICC = 0.82, 95% CI, 0.74–0.89), low error (SEM = 2°; MDC = 5.5°), and substantial agreement with video analysis [95% LoA = ±6.7°; mean difference = 1.0°]. Rater experience did not affect results (P > 0.05). The smartphone-based app offers a reliable, valid, quick, and portable method for measuring the BPA in Nordic Hamstring exercise. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.