The output angles for all joints are calculated from the YXZ Car= dan angles derived by comparing the relative orientations of the two segmen= ts.

The knee angles are calculated from the femur and the Untortioned tibia = segments, whilst the ankle joint angles are calculated from the Tortioned t= ibia and the foot segment.

In the case of the feet, since they are defined in a different orientati= on to the tibia segments, an offset of 90 degrees is added to the flexion a= ngle. This does not affect the Cardan angle calculation of the other angles= since the flexion angle is the first in the rotation sequence.

The progression angles of the feet, pelvis, thorax and head are the YXZ = Cardan calculated from the rotation transformation of the subject's Progres= sion Frame for the trial onto each segment orientation.