Acta of Bioengineering and Biomechanics Vol. 10, No. 1, 2008 Comparison of two approaches for calculation of the geometric and inertial characteristics of the human body of the Bulgarian population GERGANA NIKOLOVA*, YULI TOSHEV Institute of Mechanics and Biomechanics, Bulgarian Academy of Sciences, Bulgaria. On the basis of a representative anthropological investigation of 5290 individuals (2435 males and 2855 females) of the Bulgarian population at the age of 30–40 years (YORDANOV et al. [1]) we proposed a 3D biomechanical model of human body of the average Bul- garian male and female and compared two different possible approaches to calculate analytically and to evaluate numerically the corre- sponding geometric and inertial characteristics of all the segments of the body. In the framework of the first approach, we calculated the positions of the centres of mass of the segments of human body as well as their inertial characteristics merely by using the initial original anthropometrical data, while in the second approach we adjusted the data by using the method based on regression equations. Wherever possible, we presented a comparison of our data with those available in the literature on other Caucasians and determined in which cases the use of which approach is more reliable. Key words: body segment parameters, anthropometry, centre of mass, moments of inertia 1. Introduction An estimation of geometric and inertial parameters of the body is necessary for biomechanical analysis of human movement. Body segment parameters can be estimated in a number of different methods, including regression equations (CLAUSER et al. [2], CHANDLER et al. [3]), geometric modelling (HANAVAN [4], JENSEN [5], HATZE [6], YEADON [7]), gamma radiation scan- ning (ZATSIORSKY and SELUYANOV [8], [9]), scaling methods (DAPENA [10], FORWOOD et al. [11], ZATSIORSKY et al. [12]), computerized tomography (HUANG and WU [13], RODRIGUE and GAGNON [14], WEI and JENSEN [15], ERDMANN [16]), magnetic reso- nance imaging (MUNGIOLE and MARTIN [17]), etc. In order to be able to calculate analytically and to evaluate numerically the geometric and inertial pa- rameters of all the segments of the body, one needs to define a particular and relatively simple model of the human body. In the current study, we presented such a simple 3D biomechanical model of the average Bul- garian male and female and compared two different possible approaches to determine the measures of the quantities mentioned above. Thus, in the framework of the approach (to be denoted further by A) we cal- culated the positions of the centres of mass of the segments as well as their inertial parameters merely by using the initial original anthropometrical data, while in the second approach (to be denoted further by B), we adjusted the geometrical data by using the method based on regression equations. Comparing the data obtained in this way with data available in lit- erature on other Caucasians we demonstrated which approach is better for which characteristic of which particular segment. Let us note that for Bulgarian males and females there are no direct measurements of inertial parameters of the body segments. There- fore, the current study fills, at least partially, this gap and is a recipe for the determination of these parame- ______________________________ * Corresponding author: Gergana Nikolova, Department of Biomechanics of Motion and Telerobotics, Institute of Mechanics and Biomechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Building 4, Sofia 1113, Bulgaria. Received: February 19, 2007 Accepted for publication: December 7, 2007