ANTICIPATORY LOCOMOTOR ADJUSTMENTS FOR ACCOMMODATING VERSUS AVOIDING LEVEL CHANGES IN HUMANS

The control of locomotion has been studied from various perspectives r elated to the tasks of pattern generation, equilibrium control or adap tation to the environment. The last of these locomotor components has received comparably less attention, specifically pertaining to anticip atory adjustments. Continuing the work which has been conducted on bot h humans and cats, the present paper explores the nature of the differ ences in anticipatory locomotor adjustments for obstacle avoidance ver sus the accommodation to level changes. Six subjects walked in six dif ferent environments including no obstructions, a simple obstacle, two different level changes (a platform and stairs), and a combination of an obstacle with each respective level change. Full dynamic analyses a llowed comparison of muscle torques as well as muscle power generated and absorbed at the lower limb joints across conditions. It was found that the previously shown robust lower limb reorganization characteriz ed by a knee flexor generation strategy was upheld in all conditions w hen the obstacle was present. Pure level changes involved an augmentat ion of the ongoing hip strategy inherent In normal level walking. In t he compound environment of obstructed level changes, subjects chose to combine an augmentation of hip Flexor power with a reorganization to active knee flexion. The results lire discussed from the point of view of general principles of mechanical coordination and the exploitation of intersegmental dynamics for foot transport.