Fig. 1

Lower extremity retro-reflective marker placement used during three-dimensional motion trials. The calibration markers were placed bilaterally on the lateral and medial malleolus, the medial and lateral femoral epicondyles, the greater trochanter of the femur, and on the feet over the first and fifth metatarsal heads. Tracking markers were positioned on the iliac spines, the anterior and posterior superior iliac crests, the acromion process, cervical vertebrae 7, thoracic vertebrae 10, Sternum Xiphisternal Joint, proximal end of head and three on the posterior aspect of the foot. Additionally, four hard light-weight plates each with four tracking markers were placed on the right and left thighs and shanks