The primary goal of the proposed study is to identify the contributions of the amount of task-specific practice on locomotor (i.e., walking) recovery in patients with (\> 6 Months) traumatic brain injury (TBI). The investigator will do this by building on our previous work directed towards identifying the essential exercise training parameters that maximize locomotor recovery. Consistent with principles of motor learning and exercise physiology, the investigator contend that certain training (i.e., dosage) parameters of physical rehabilitation, including the type (specificity) and amount of task practice, are critical to mobility outcomes following neurological injury. Previous work suggests these training parameters may influence locomotor recovery in patients with other neurological disorders (i.e., stroke), although few studies have attempted to delineate similar contributions of amount of task-specific practice in neurologic injury. Indeed, no studies have carefully controlled these training parameters during physical rehabilitation of patients with neurologic injury, and such interventions are rarely utilized in the clinical setting. Reasons for these knowledge gaps from other rehabilitation studies to patients with neurologic injury or lack of clinical implementation are unclear, but may be due to adherence to traditional rehabilitation theories. One concern is that practicing only stepping tasks reduces attention towards hallmark physical impairments following neurologic injury, such as loss of strength or postural stability, which are considered primary determinants of decreased mobility. Only a few studies have addressed whether providing only structured stepping training can mitigate these impairments without their explicit practice, but not in the neurologic injury population. A related concern is that focused stepping training without significant attention towards impairments or gait quality may exaggerate altered movement strategies, which could be reinforced with repeated practice. However, there is little data to suggest "worsening" of abnormal gait patterns following high intensity training. Rather, recent findings suggest patients demonstrate more normal kinematics. If focused task specific (i.e., stepping) training is to be applied clinically, participant must delineate its contributions towards improving locomotor function, and their effects on underlying impairments and gait kinematics.

Central hypotheses are that stepping training in TBI results in:1) greater locomotor gains as compared to non-specific interventions; 2) gains in selected impairments underlying gait dysfunction (i.e., strength and metabolic capacity and efficiency); and, 3) improvements in gait quality. To test these hypotheses, the proposed crossover, assessor-blinded, randomized clinical trial (RCT) is designed to test the effects of specificity of rehabilitation training applied early-post-stroke. In this RCT, patients \> 6 post-TBI will be allocated ≤ 15 sessions over approximately 4-5 weeks of high-intensity stepping training or conventional therapy. Importantly, training intensity will be held constant to account for this potential confounding factor. Blinded assessments will be performed prior to and following each training paradigm.