## Body Coordinate System Table A21

Let an orthogonal coordinate system B be defined by the intersection of the three principal planes of the body passing through the center of gravity in the standing position as shown in Fig. A.2.1. The location of the center of mass (gravity) of the body is measured along the b3 axis from top of the head (L3), along the b1 axis from the back plane (L1), and along the b2 axis from the anterior superior spine of the ilium (L2) as shown in Fig. A.2.2. The body positions identified with symbols 1, 2, 3, and 4 are illustrated in Fig. A.2.3. The parameters I1, I2, and I3 denote the mass moment of inertia elements along the b1, b2, and b3, respectively.

 Position L1 L2 L3 Ii I2 I3 Subject 1: Age, 29; height, 72.2 1 3.62 in.; weight 173.5 lb 5.31 32.2 132 119 13.1 2 3.52 5.31 29.9 174 159 12.5 3 3.34 5.31 29.5 172 135 41.9 4 7.70 5.31 23.9 41.4 37.3 29.9 Subject 2: Age, 23; height, 67.4 1 3.50 in.; weight, 147.3 lb 4.25 29.8 95.6 81.9 10.3 2 3.49 4.25 27.5 126 110 10.2 3 3.18 4.25 27.2 125 90.3 30.0 4 7.03 4.25 21.7 32.9 30.4 21.5 Subject 3: Age, 33; height, 73.3 1 3.81 in.; weight, 203 lb 5.61 31.8 144 129 14.2 2 3.67 5.61 29.4 188 172 13.8 3 3.56 5.61 29.5 187 142 51.2 4 7.75 5.61 23.4 48.9 41.9 36.7

Note: AH lengths (Li, L2, L3) are inches (in.; multiply by 2.54 to convert to centimeters, cm) and moment of inertia (I1, I2, I3) in lb-in.-s2 (multiply by 0.11298 to convert to kg-m2).

frontal sagittal plane posterior right frontal b

posterior right

sagittal plane

Figure A.2.1. Body coordinate system.

Figure A.2.1. Body coordinate system.

Figure A.2.2. Reference landmarks for the location of center of gravity.

Figure A.2.2. Reference landmarks for the location of center of gravity.

Figure A.2.3. Body positions.

Matsuo et al. (1995) proposed the following equations for relating the moment of inertia I1 and I2 of adolescent boys to their height H (in m) and weight W (kg). These equations may provide reasonably accurate results for other subpopulations.