title: The effect of the stability threshold on time to stabilization and its reliability following a single leg drop jump landing.
abstract: We aimed to provide insight in how threshold selection affects time to stabilization (TTS) and its reliability to support selection of methods to determine TTS. Eighty-two elite youth soccer players performed six single leg drop jump landings. The TTS was calculated based on four processed signals: raw ground reaction force (GRF) signal (RAW), moving root mean square window (RMS), sequential average (SA) or unbounded third order polynomial fit (TOP). For each trial and processing method a wide range of thresholds was applied. Per threshold, reliability of the TTS was assessed through intra-class correlation coefficients (ICC) for the vertical (V), anteroposterior (AP) and mediolateral (ML) direction of force. Low thresholds resulted in a sharp increase of TTS values and in the percentage of trials in which TTS exceeded trial duration. The TTS and ICC were essentially similar for RAW and RMS in all directions; ICC's were mostly 'insufficient' (<0.4) to 'fair' (0.4-0.6) for the entire range of thresholds. The SA signals resulted in the most stable ICC values across thresholds, being 'substantial' (>0.8) for V, and 'moderate' (0.6-0.8) for AP and ML. The ICC's for TOP were 'substantial' for V, 'moderate' for AP, and 'fair' for ML. The present findings did not reveal an optimal threshold to assess TTS in elite youth soccer players following a single leg drop jump landing. Irrespective of threshold selection, the SA and TOP methods yielded sufficiently reliable TTS values, while for RAW and RMS the reliability was insufficient to differentiate between players.
authors.affiliation: MOVE Research Institute Amsterdam, Department of Human Movement Sciences, VU University, Amsterdam, The Netherlands; Department of Orthopaedic Surgery, Atrium Medical Center, Heerlen, The Netherlands. Electronic address: dpfransz@gmail.com.
authors.forename: Duncan P
authors.initials: DP
authors.lastname: Fransz
authors.affiliation: MOVE Research Institute Amsterdam, Department of Human Movement Sciences, VU University, Amsterdam, The Netherlands; Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Arnold
authors.initials: A
authors.lastname: Huurnink
authors.affiliation: Adidas miCoach Performance Centre, AFC Ajax, Amsterdam, The Netherlands.
authors.forename: Vosse A
authors.initials: VA
authors.lastname: de Boode
authors.affiliation: MOVE Research Institute Amsterdam, Department of Human Movement Sciences, VU University, Amsterdam, The Netherlands.
authors.forename: Idsart
authors.initials: I
authors.lastname: Kingma
authors.affiliation: MOVE Research Institute Amsterdam, Department of Human Movement Sciences, VU University, Amsterdam, The Netherlands.
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
mesh_terms: D000293:Adolescent; D001835:Body Weight; D002648:Child; D015444:Exercise; D006801:Humans; D007866:Leg / Q000502:physiology*; D004856:Postural Balance; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012916:Soccer; D012984:Software; D013177:Sports; D013314:Stress, Mechanical
keywords: Dynamic; Force plate; Force platform; Outcome measure; Postural control