Comparing methods of estimating the total body centre of mass in three-dimensions in normal and pathological gaits

It is common clinical practice to estimate the position of the total body c entre of mass (CM) as being a fu;ed point in the centre of the pelvis (CP). Previous work has shown that there are significant differences between CP and the estimate of the position of CM from the second integral of ground r eaction force data (GRF). In this study the CM was determined during an ent ire gait cycle in II able-bodied subjects (6 adults and 5 children) and 5 c hildren with lumbosacral myelomeningocoele using both methods (GRF and CP). The CM was also estimated using a full body multi-segment kinematic model (KM). In agreement with previous work the excursion of CP showed significan t differences from that of GRF. CP always had a larger total excursion than GRF. KM however, showed no significant differences from GRF in any of the three orthogonal directions in any group. These results show that the use o f a full body kinematic model gives a better representation of the CM than does a fixed point in the pelvis, especially in pathological gait patterns. (C) 1999 Elsevier Science B.V. All rights reserved. PsycINFO classificatio n: 2330.