estimation of centre of gravity movements in sitting posture: application to trunk backward tilt

the aim of this study was to highlight, in sitting posture, the value of distinguishing between the movements of the vertical projection of the centre of gravity (cg_v) and its difference from the centre of pressure (cp−cg_v). a protocol for healthy, young, trained adults, consisting in tilting their trunk backward or keeping it vertical was used. a frequency analysis shows that statistically significant effects were only seen on cp−cg_v movements: the rms increased by 37% (p=0.004), while the mpf decreased by 5% (p=0.016), suggesting an increased muscular activity in these tilting postures. in contrast, no statistically significant effects on cp and cg_v were reported. these data highlight the advantage, in sitting posture, of splitting overall cp displacements into basic components (i.e. cg_v and cp−cg_v), each of them having a biomechanical significance.