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.