Precision of the estimation of human limb inertial parameters

Repeat measurements were made by 2 operators on a group of 50 physically active subjects (age, 20.7 years±1.8; males: height 1.780 m+0.043, mass, 78.09 kg+9.30; females: height, 1.680 m+0.064, mass, 66.67 kg+6.67) to determine the precision with which the subjects' limb segment inertial parameters could be estimated. Segmental inertial parameters were determined using 3 techniques, 2 of which involved modeling segments as geometric solids, and a 3rd which used the equations of Zatsiorsky et al. (1990). Precisions were high for all 3 techniques, with little difference between inter- and intra-operator precisions. The lowest precisions were obtained for the hands and feet. For these segments the use of repeat measures to improve precision is recommended. These results imply that with similarly trained measurers, comparison of inertial parameters determined using the same protocol but obtained by different operators is appropriate, and that it is viable to have 2 measurers taking measurements on the same subject to accelerate data collection.