Anteroposterior displacement behavior of the center of pressure, without visual reference, in postmenopausal women with and without lumbar osteoporosis

OBJECTIVE The aims of this study were to evaluate the anteroposterior displacement behavior of the center of pressure without any visual reference and determine its relationship with knee muscle strength and reports of falls in postmenopausal women. Among those with osteoporosis, the specific objective was to evaluate the correlation of thoracic kyphosis and vitamin D with center of pressure displacement. METHODS This was a cross-sectional observational study without intervention. The assessments were performed on 126 postmenopausal women (aged 55-65 years) who were grouped according to their lumbar bone density into osteoporosis and control groups. Center of pressure was evaluated on a force platform (100 Hz frequency and 10 Hz filter), with the subjects standing on both feet with eyes closed for 60 seconds. Knee muscle strength was evaluated using an isokinetic dynamometer in concentric/concentric mode at a velocity of 60°/s. In the osteoporosis group, vitamin D was assayed, and the thoracic spine was radiographed. RESULTS In the control group, there was a correlation between the center of pressure and knee strength (r = 0.37; p<0.003). Reports of falls were not associated with center of pressure displacement (p = 0.056). In the osteoporosis group, thoracic kyphosis and vitamin D levels were not correlated with the center of pressure. CONCLUSION Anteroposterior center of pressure displacement without visual influence was not associated with falls, thoracic kyphosis or vitamin D in the osteoporosis group. Only knee muscle strength was associated with center of pressure displacement in the control group.