Kinematics of the Foot During Slips

Slip and fall accidents are often listed among the leading generators of injuries. The goals of this study were to (1) describe the foot kinematics during unexpected slips, and (2) to compare the foot kinematics during gait in unexpected slippery environment and when warnings of slippery environments are provided. Five participants walked on dry and glycerol-contaminated floors, while varying the participant's a-priori knowledge of the floor's contaminant condition. Foot kinematics were recorded at 500 Hz from 5 Optotrak LEDs placed on the slipping foot. In unexpected slips, all participants slipped and fell, whereas under the warning conditions, all participants slipped and recovered. Foot kinematics were affected by the warning conditions. More specifically, the heel's vertical velocity just prior to impact and foot-floor angle at heel contact decreased in alert/known slippery environments compared to unexpected slips. Slip distances and velocities were greater in unexpected slips. Finally, the impact of recovery attempts on the heel's kinematics were evident earlier in stance when participants knew or suspected the floor was slippery. Thus, the a-priori perception of slippery surfaces affects the foot kinematics and outcome of slipping.