Joint kinetics of the ankle and knee when running over obstacles

Aim. When running over obstacles of increasing height, heel-strike (HS) runners switch to a forefoot (FF) landing pattern once a critical obstacle height is reached. The primary purpose of this study was to determine whether ankle or knee joint kinetic variables trigger the gait change from a HS to a FF striking pattern as obstacle height increases. Methods. Ten subjects were filmed from the sagittal plane as they ran at their preferred running speed over a force platform during 6 obstacle height conditions ranging from 10% to 22.5% of standing height, as well as an additional baseline condition with no obstacle (0%). An inverse dynamics approach was utilized to calculate ankle and knee joint kinetics at each condition. Results. Differences in joint kinetics did not occur until a height was reached at which the landing strategy changed from a HS to a FF landing pattern. Most differences occurred at the ankle joint, at which there was a greater maximum plantar flexor moment and a greater amount of energy absorbed when obstacles of sufficient height to require a FF landing pattern were negotiated. Conclusion. Although no variables were found which met all of the criteria necessary to be considered a determinant of the gait transition, there were variables which distinguished between a HS and FF strike landing pattern as obstacle height increased.