The influence of multiple obstacles in the travel path on avoidance strategy.

Obstacle avoidance strategy was analysed as participants were subjected to varied quantities and positions of obstacles in their travel path. Kinematic data were collected with three optoelectric cameras sampling at 100 Hz. Calculated from this data were toe-elevation and take-off distance for both lead and trail limbs. Each subject completed a total of 120 randomly assigned trials (15 repetitions in each of eight test conditions). Test conditions were as follows: no obstacle (C1), a single obstacle at 0 (C2), 1 (C3), 1.5 (C4), and 2 m (C5) positions and double obstacles at 0 and 1 (C6), 0 and 1.5 (C7) and 0 and 2 m (C8) positions. Avoidance strategy was defined in terms of take-off distance and toe-elevation at obstacle crossing. Single obstacle trials demonstrated that take-off distance and toe-elevation are gait parameters, which are controlled in successful obstacle clearance. Double obstacle trials revealed that presence and position of a second obstacle in the travel path influences trail limb take-off distance for both first and second obstacles. Copyright 2002 Elsevier Science B.V.