How long is required to undertake step variability analysis during running? A pilot study

Abstract

BACKGROUND: The accurate assessment of step variability remains problematic. OBJECTIVE: To determine the minimum time required for assessing spatiotemporal variability during continuous running. METHODS: Seventeen endurance runners performed a running protocol on a treadmill, with a 3-min recording period at 12 km/h. Spatiotemporal parameters (contact and flight times, step length and step frequency) were measured using the OptoGait system and step variability was considered for each parameter, in terms of within-participants standard deviation (SD) and coefficient of variation (CV%). Step variability was calculated over 6 different durations: 0–10 s, 0–20 s, 0–30 s, 0–60 s, 0–120 s and 0–180 s. RESULTS: The repeated measures ANOVA revealed no significant differences between measurements in mean spatiotemporal gait parameters (p⩾ 0.396, ICC ⩾ 0.90 in all parameters). The post-hoc analysis confirmed no significant differences in step variability (of each spatiotemporal parameter) between measurements. The Bland-Altman limits of agreement method showed that longer recording intervals yield smaller systematic bias, random errors, and narrower limits of agreement. CONCLUSIONS: The duration of the recording interval plays an important role in the accuracy of the measurement (i.e. variability in spatiotemporal gait parameters), with longer intervals (180 s) showing smaller systematic bias and narrower limits of agreement than shorter intervals (10 s, 20 s, 30 s, 60 s or 120 s).