The Concept of Shaping Applied to Locomotor Interventions: Clinical and Robotic Strategies to Facilitate and Progress Variable Stepping Training at Higher Intensities.

High-intensity training (HIT) focused on stepping practice consistently improves clinical locomotor outcomes in individuals with neurologic injury. However, traditional HIT approaches typically do not target underlying impairments, and gains in non-locomotor tasks (ie, balance and transfers) or daily stepping are limited. One strategy to address these limitations involves providing HIT in variable contexts by progressively increasing locomotor demands across diverse environments while targeting specific biomechanical deficits (ie, limb-swing, propulsion, stance, and postural stability). This approach parallels the concept of "shaping" used successfully in constraint-induced movement therapy trials pioneered by Dr. Steven Wolf. The rapid progression of variable, difficult stepping tasks during HIT produces gains in multiple locomotor and non-locomotor outcomes, although, importantly, the accelerated progression of task demands and acceptance of movement variability represent key departures from conventional rehabilitation frameworks emphasizing gait quality. Together, this focus on progression and variability is likely responsible for the observed gains. In this issue honoring Dr. Steven Wolf, we delineate the shaping principles applied to locomotor rehabilitation following neurologic injury. We outline the rationale for HIT in variable contexts, explain how biomechanical targeting guides intervention progression, and present evidence detailing its observed efficacy in improving clinical and community mobility outcomes. We also describe how advanced robotic technology can further enhance locomotor outcomes by applying progressive resistance to target specific locomotor deficits. By integrating principles of biomechanics with long-standing theories in motor learning, we believe HIT in variable contexts can further harness the neural plasticity of the nervous system to maximize locomotor function following neurologic injury.