Variability of centre of pressure movement during gait in young and middle-aged women

•Stance phase was divided according to vertical ground reaction force behaviour.•Centre of pressure movement variability was used for dynamic stability assessment.•The highest variability was found in subphases loading response and preswing.•Centre of pressure movement variability was higher in middle-aged subjects.

The variability of the centre of pressure (COP) movement is a tool that is often used for stability assessments during standing; however, this variable can provide relevant findings during dynamic conditions, which are more related to fall risks. The aim of this study was to investigate age-related differences in the variability of COP movement. Healthy young (younger group – 25 subjects, age 22.2 ± 1.8 years) and middle-aged (elder group – 25 subjects, age 56.6 ± 4.9 years) females participated in this study. The ground reaction forces and COP movement during walking at a self-selected speed were recorded using two force platforms. Each stance phase was divided into four subphases: loading response (LR), mid-stance (MSt), terminal stance (TSt) and preswing (PS). Standard deviations of the medial–lateral, anterior–posterior and total COP displacements were assessed. For statistical comparisons, one-way ANOVA and the Bonferroni post-hoc test were used. These results showed significantly higher COP movement variability in selected variables in the PS, LR and MSt subphases in the elder group (p < 0.05) compared with the younger group; no differences were found in the TSt subphase. A comparison of the subphases within the groups revealed significant differences (p < 0.001 for all cases and both groups) between the parameters in the LR × MSt, LR × TSt, MSt × PS and TSt × PS subphases. The LR and PS subphases showed significantly higher values for the variability parameters.