INERTIAL CHARACTERISTICS OF CHILDREN AND THEIR APPLICATION TO GROWTH STUDY

The water displacement method was used in this study to obtain volume distribution data on limb segments. A mathematical method was then app lied to those data to calculate the values for centre of gravity, radi us of gyration, principal moment of inertia, and volume. The results s howed the water displacement method is not sensitive to random error, while giving a good estimation of inertial properties. Centre of gravi ty, expressed as percentage of segment length, has a very small varian ce; the variance of radius of gyration was even smaller. These two var iables show sex-related differences, the former also displaying differ ences relating to age, especially for multi-segment units such as the forearm with hand. The principal moment of inertia and volume were hig hly correlated with anthropometric variables. Volume ratios had signif icant sex and age differences, absent for the absolute value for volum es. Since the results demonstrated characteristics absent from convent ional anthropometric investigation, the interial properties may find a n application as new indicators of children's growth. It has also note d that the results from previous studies had different results for som e inertial characteristics, indicating a need for further studies of t he inertial properties of the human body.