Effects of anthropometry, age and sex on center of pressure displacement evoked by small trunk perturbations in balance tests

Purpose Balance control can be evaluated by studying the displacement of the center of pressure (CoP) during dynamic posturographic trials. However, differences in anthropometric characteristics may affect the measurement and increase intersubject variability, possibly leading to misinterpretation. This study evaluates how sex, age, and anthropometric characteristics (weight, height, and foot length) influence the CoP displacement to postural perturbations. Methods Seventy-two healthy subjects, 31 women and 41 men, were subjected to five small impulsive perturbations applied to their back. Balance performance was quantified by three CoP parameters: the ratio between the maximum CoP displacement and the impulse of the perturbation (Delta CoPn), the latency (Lat), and the duration (Dur) of the CoP response. Results A linear regression analysis evidenced that body weight and height exhibited a negative and positive relation with Delta CoPn, respectively, which explained 48% of the Delta CoPn variability. These relations were confirmed by simulations with a single-link biomechanical model. On the other hand, the latency and the duration of the CoP response were affected neither by the anthropometric characteristics nor by sex. Conclusion Findings from the present study have an impact on test protocols, especially when comparing data collected from heterogeneous populations, in which case normalization with respect to the subjects' height and weight may be necessary to use the Delta CoPn as a postural performance index.