INERTIAL PROPERTIES OF THE HUMAN TRUNK OF MALES DETERMINED FROM MAGNETIC-RESONANCE-IMAGING

The purpose of this study was to evaluate the segmental parameters of the human trunk of males in vivo using magnetic resonance imaging (MRI ). In addition, the efficacy of volumetric estimation and existing pre diction formulas to produce segmental properties similar to those prod uced by MRI was evaluated. As opposed to finding one representative no rmal value for these parameters, a range of normal values was defined. For instance, the average trunk mass was 42.2% +/- 3.5% (x +/- SD) of body mass, but values ranged from 35.8% to 48.0%. To account for segm ent parameters more accurately, specific anthropometric measures need to be considered in addition to overall measures of body height and ma ss. These specific measures included segment length, circumference, wi dth, and depth. Studies reporting general percentages based on height and/or mass were found to be inadequate predictors of segmental parame ters of the trunk compared with MRI estimates. Volume based estimates, which assume a uniform density distribution within a segment, were fo und to correspond closely to MRI values except for the thorax. However , the use of density values reflective of the living in vivo state wou ld likely alleviate this disparity, thus indicating that the volumetri c technique may be effective for deriving segmental parameters for lar ge segments of the trunk. Future research should adopt noninvasive tec hniques such as MRI and/or volumetric estimation to enhance the predic tability of segmental parameters of the body for specific population g roups characterized by gender, developmental age, body type, and fitne ss level. Further efforts should be made to establish standardized bou ndary definitions for trunk segments to avoid unnecessary confusion, f rom which substantial errors may be introduced into biomechanical link ed-segment analyses of human movement.