Comparison of kinetic strategies for avoidance of an obstacle with either the paretic or non-paretic as leading limb in persons post stroke.

The task of stepping over obstacles is known to be particularly risky for persons post stroke. A kinetic analysis informing on the movement strategies used to ensure clearance of the leading limb over an obstacle is, however, lacking. We examined obstacle avoidance strategies in six community dwelling stroke survivors comparing the use of paretic and non-paretic limb as the leading limb for clearance over obstacles measuring 7.5% and 15% of their total leg length. Subjects were able to increase foot clearance height in both limbs in order to avoid the two obstacles. Obstacle clearance with the non-paretic limb leading was associated with positive knee flexor work that increased when stepping over each obstacle, thus showing a normal knee strategy that flexes both the knee and the hip for foot clearance. There was also slightly increased hip flexor contribution for non-paretic obstacle clearance that was the same for both obstacle heights. When the paretic limb led during obstacle clearance, there was also evidence of an increased knee flexor moment, suggesting a residual knee strategy, but it was less pronounced than for the non-paretic limb and was assisted by greater vertical hip elevation and additional positive hip flexor work that both gained greater importance with increased obstacle height. These findings suggest that rehabilitation should explore the ability to improve the residual, but less powerful, knee flexor strategy in the paretic limb in specific patients, with further promotion of a hip flexor and limb elevation strategy depending on patient deficits and obstacle height.