title: Movement variability cannot be determined reliably from no-marker conditions.
abstract: We sought to quantify the proportion of total variability due to movement variability in digitizing marker and no-marker conditions in treadmill running. Manually digitized markers gave variabilities in joint angles within 0.4 degrees of those from auto-tracking. Marker conditions allowed reliable estimation of movement variability by an experienced operator; the contribution of movement variability to total variability, expressed by omega-squared, had averages across the four operators of 97% for the knee angle and 93% for the hip. The no-marker condition did not allow reliable estimation of movement variability-the above figures fell, respectively, to 72% and 48%-and cannot be recommended. The group design in the marker condition produced omega-squared values of 97% knee and 91% hip, showing excellent objectivity (inter-operator reliability). However, without markers, these values fell to 47% and 15%, respectively, indicating that movement variability cannot be assessed objectively in no-marker conditions.
authors.affiliation: School of Physical Education, University of Otago, Dunedin, New Zealand. rbartlett@pooka.otago.ac.nz
authors.forename: Roger
authors.initials: R
authors.lastname: Bartlett
authors.forename: Melanie
authors.initials: M
authors.lastname: Bussey
authors.forename: Nick
authors.initials: N
authors.lastname: Flyger
mesh_terms: D000328:Adult; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D012420:Running / Q000502:physiology*; D014741:Video Recording / Q000379:methods