Download 3D Static Strength Prediction Program Version 6.0.6 User`s Manual

Page 43
3D Static Strength Prediction Program Version 6.0.5
6.7.3.7
Trunk Flexion Angle
The trunk flexion angle is the angle between the
projection of the trunk axis (the center of the hips to
the center of the shoulders) onto the Z-Y plane and
the positive Y axis (Figure 6.22). When standing
straight, the trunk angle is 90 degrees. If the trunk is
level with the horizontal plane (ground), the angle
is 0°. If the trunk is flexed below the horizontal
plane, the angle is negative. The range of motion
for this angle should be such that the angle between
the trunk and the upper legs is between 40 and 100
degrees.
6.7.3.8
Trunk Lateral Bending Angle
The trunk lateral bending angle is formed between the trunk axis and the Z-Y plane. If the torso
is bent towards the positive X axis, the angle is positive. If the torso is bent toward the negative X axis,
the angle is negative. Referring to Figures 6.23 a
and b, note that this convention holds whether the
torso is bent or erect. The range of motion for lateral bending is limited to +/-40 degrees.
Note that within the biomechanical model the
trunk is formed by the pelvis and the torso links
which are each assigned separate angles based on
the entered trunk flexion angle according to an algorithm derived from empirical data (Anderson,
1983). The two links are visible in the human
graphics in the display view windows.
(a)
Figure 6.22: Trunk flexion angle
(b)
Figure 6.23: Lateral bending angle with
stooped and non-stooped torsos
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