RecruitingProcedureHigh-Intensity, Dynamic-stability Gait Training in People With Multiple SclerosisThe goal of this clinical trial is to improve walking speed, balance, and walking in the community for people with multiple sclerosis. This trial involves intense exercise combined with walking on a shaky treadmill. Walking on a shaky treadmill helps to practice balance and intense exercise promotes the ability to walk faster and farther. In this study, participants will train with a combination of high or low intensity, and with a stable or shaky treadmill. Walking speed and endurance, balance while walking and the number of steps taken in the community will be measured before, half way through the training (15 sessions), after training (30 sessions) and six months after training.