High Intensity Step Training After Traumatic Brain Injury

Inclusion Criteria:

* TBI definition: damage to brain tissue caused by an external mechanical force as evidenced by loss of consciousness (LOC) or post traumatic amnesia (PTA) due to brain trauma or by objective neurological findings that can be reasonably attributed to TBI on physical examination or mental status examination
* Less than 6 months post injury at time of consent
* Weight less than 298 pounds and height less than 6'2" (based on treadmill contraindications)
* Intact skin (no open lesions/bandages) in the area of treadmill harness contact
* Able to walk ten feet requiring the physical assistance of not more than two people and/or bracing, assistive devices
* Impaired walking speed of \< than 1.4 meters/second
* Ability to follow directions/standardized instructions
* Minimum 18 years of age at consent
* Completing or have completed initial inpatient rehabilitation for TBI
* O-Log score of at least 20
* Medically cleared for HIST by a physician

Exclusion Criteria:

* Uncontrolled cardiopulmonary, metabolic, or infectious disorder
* History of orthopedic or additional neurological disorder that limited motor function before TBI
* Any reason that, in the opinion of the study investigators or medical team, would interfere with completing the study protocol such as behavioral concerns
* Uncontrolled seizure disorder
* Pregnant or lactating females
* Current participation in any other interventional trials
* History of an untreated or a poorly controlled psychiatric condition such as depression, schizophrenia, or bipolar disorder