title: Reproducibility and validity of the myotest for measuring step frequency and ground contact time in recreational runners.
abstract: The purpose of this study was to assess the reproducibility (test-retest reliability and agreement) and concurrent validity of the Myotest for measuring step frequency (SF) and ground contact time (GCT) in recreational runners. Based on a within-subjects design (test and retest), SF and GCT of 14 participants (11 males, 3 females) were measured at three different running speeds with the Myotest during two test sessions. SF and GCT were also assessed with a foot-mounted accelerometer (Gold Standard, previously validated by comparing to force plate data) during the first test session. Levels of test-retest reliability and concurrent validity were expressed with intraclass correlation coefficients (ICC), agreement with standard errors of measurement (SEM). For SF, test-retest reliability (ICC's > 0.75) and agreement of the Myotest were considered as good at all running speeds. For GCT, test-retest reliability was found to be moderate at a running speed of 14 km/h and poor at speeds of 10 and 12 km/h (ICC < 0.50). Agreement of the Myotest for GCT at all three running speeds was considered not acceptable given the SEM's calculated. Concurrent validity of the Myotest with the foot-mounted accelerometer (Gold Standard) at all three running speeds was found to be good for SF (ICC's > 0.75) and moderate for GCT (0.50 < ICC's < 0.75). The conclusion of our study is that estimates obtained with the Myotest are reproducible and valid for SF but not for GCT.
authors.affiliation: Department of Orthopaedic Surgery, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Vincent
authors.initials: V
authors.lastname: Gouttebarge
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Robin
authors.initials: R
authors.lastname: Wolfard
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Nouschka
authors.initials: N
authors.lastname: Griek
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Cornelis J
authors.initials: CJ
authors.lastname: de Ruiter
authors.affiliation: Vintta | Research and Consultancy for Sport Health, Almere, The Netherlands.
authors.forename: Julitta S
authors.initials: JS
authors.lastname: Boschman
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands. ; King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
keywords: agreement; concurrent validity; ground contact time; step frequency