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Obstacle avoidance during human walking: effects of biomechanical constraints on performance
Hubertus J van Hedel1, Volker Dietz
1Spinal Cord Injury Center, Balgrist University Hospital, Forchstrasse 340, CH-8008 Zurich, Switzerland. hvanhede@balgrist.unizh.ch
Objective:
To determine whether fixation of the ankle joint, the knee joint, or both increasingly affects the performance of a newly learned task, that is, stepping over an obstacle.
Design:
Randomized trial.
Setting:
Research laboratory of a university hospital in Switzerland.
Participants:
Eighteen healthy, young volunteers.
Intervention:
Subjects walked on a treadmill and, with reduced vision, stepped with the right leg over a randomly approaching obstacle. They adapted to the task during the 2 runs. In the third run, fixating orthoses of the ankle-foot (AFO), knee (KO), or both (KAFO) were attached to the left leg.
Main Outcome Measure:
The "performance" consisted of leg muscle activity, joint movements, swing phase duration, and the clearance between the foot and the obstacle. The changes within runs (adaptation) and between runs (eg, transfer) were evaluated.
Results:
The attached orthoses caused a reduced transfer of performance in the KAFO and KO between runs 2 and 3. No differences in the rate of adaptation were observed among the 3 groups during the third run.
Conclusions:
A movement restriction of the supporting leg worsened the performance of the contralateral leg in a locomotor task. Performance was more affected by knee-joint fixation than by ankle-joint fixation alone and, consequently, the need for relearning is greater.