Adults aged 18-65 with TBI. At Week 1 after baseline, participants will begin study intervention on the C-Mill with augmented/virtual reality (AR/VR) guidance. Starting at Week 2, the study intervention on C-Mill will be repeated 3 sessions/week for 8 weeks.

Each one hour session will include about 15 minutes of standing balance training, about 5 minutes of stepping balance training and about 30 minutes of walking training on the C-Mill with AR/VR feedback.

Adults aged 65 and older with TBI. At Week 1 after baseline, participants will begin study intervention on the C-Mill with augmented/virtual reality (AR/VR) guidance. Starting at Week 2, the study intervention on C-Mill will be repeated 3 sessions/week for 8 weeks.

Each one hour session will include about 15 minutes of standing balance training, about 5 minutes of stepping balance training and about 30 minutes of walking training on the C-Mill with AR/VR feedback.

Adults aged 18-65 with TBI. At Week 1 after baseline, participants will begin study intervention on the C-Mill without augmented/virtual reality (AR/VR) guidance. Starting at Week 2, the study intervention on C-Mill will be repeated 3 sessions/week for 8 weeks.

Each one hour session will include about 15 minutes of standing balance training, about 5 minutes of stepping balance training and about 30 minutes of walking training on the C-Mill without AR/VR feedback.

Treadmill training system that is a combination of an instrumented treadmill, front display, and a floor projector, allowing functional gait and balance training. The AR/VR feedback will include computer generated obstacles and objects projected as images on the treadmill. Participants will be asked to use these projections as stepping cues and step on some images of objects while avoiding stepping on the images of obstacles.

Recruitment rate is defined as the number of patients recruited on average for one month in one site.

Enrollment Rate defined as the percentage of recruited participants who enrolled in the study.

Retention rate defined as the percentage of enrolled participants who completed the study.

FES-I is a 16-item self-assessment of fear of falls in different situations. Each item is ranked on a 4-point Likert scale ranging from 1 (Not at all concerned) to 4 (Very concerned). The total score is the sum of responses and ranges from 16 to 64; lower scores indicate lower fear of falls. A decrease in scores indicates fear of falls decreased over the observational period.