Height- and body-mass-specific reference values and percentile curves for spatiotemporal gait parameters in school-aged children from Zagreb, Croatia

Background Paediatric gait reference values are organised according to chronological age and sex, although children of the same age may differ in body size. This study aimed to establish body-height- and body-mass-specific reference values and smoothed percentile curves for spatiotemporal gait parameters and to examine whether body height and body mass provide additional information beyond chronological age and sex. Methods This cross-sectional study included 1,045 children aged 6–14 years from four elementary schools in Zagreb, Croatia, comprising 506 boys and 539 girls. Participants completed six barefoot walking trials at a self-selected speed along a 12 m walkway equipped with a Zebris FDM 1.5 pressure platform. Reference values were calculated separately for boys and girls within 10 cm height intervals and 5 kg body-mass intervals, with empirical percentiles from the 5th to the 95th smoothed using locally weighted scatterplot smoothing. Secondary nested regression models examined the incremental information provided by body height beyond exact chronological age and sex and by body mass after accounting for height. Results Parameter-specific sample sizes ranged from 980 to 1,045. Across body-height categories, step and stride length and step and stride time increased progressively, whereas cadence decreased and gait velocity remained comparatively stable. Adding body height to age- and sex-based models increased explained variance most for step length (Δ adjusted R 2 = 0.088) and stride length (Δ adjusted R 2 = 0.084), with a smaller increment for cadence (Δ adjusted R 2 = 0.030). Body mass contributed little additional explained variance for step and stride length after height was included, but larger increments were observed for step width (Δ adjusted R 2 = 0.051) and support-related gait-cycle phases (Δ adjusted R 2 = 0.043–0.053). Conclusion Body height provided additional information beyond chronological age and sex for absolute step and stride length and, to a lesser extent, gait rhythm. Beyond height, body mass added small, outcome-specific information for step width and support-related phases. Height- and body-mass-specific references may supplement, but not replace, age- and sex-specific paediatric gait references; their clinical value remains to be established, and they apply only to barefoot walking at self-selected speed measured with a comparable platform and protocol.