Fig. 2.

Schematic illustration of the experimental setup for inducing unannounced slips in gait. A slip is induced by releasing two low-friction movable platforms. Each of the two moveable platforms is mounted on a frame with four linear bearings, and the frame was bolted to two force plates to measure the ground reaction force. The low-profile movable platforms (and the force plates beneath, not shown here) were embedded in a 7-m walkway with decoy platforms (not shown) to reduce its visibility. The right- and left- side moveable platforms can be unlocked electronically after the landing of the corresponding foot. A set of 28 light-reflective markers were placed on bilateral upper and lower extremities, torso, and platforms. Their spatial positions were captured by an 8-camera motion capture system. The subjects were required to wear a safety harness which is individually adjusted to prevent a fall to the ground. A load cell was used to measure the force exerted on the harness.