Though humans have optimized walking to minimize their energy expenditure, it is still energetically expensive, even for healthy individuals. This naturally poses a further challenge for unhealthy individuals, especially when coupled with unstable walking gait. Thus, our goal is to create an unpowered, adaptive, rehabilitative, medical device that assists in strengthening muscles and promoting self-sufficiency during walking. Our device consists of a belt worn above the hips and a strap sitting below the knee of the affected leg. A rope and elastic band system connected between the hip and the knee utilizes a mechanical pulley-lock mechanism. This mechanism allows the device to control the resistance created by the elastic bands which stretch and relax along the leg as a person walks. The elastic bands store and release energy to relieve the strain in leg muscles, particularly in the hamstrings and quadriceps during walking. From rehabilitating athletes with torn ACLs to assisting the elderly with muscle atrophy, we envision our device to be used for a broad spectrum of patients and for a variety of reasons. Our hope is to contribute to a decreased recovery time for the injured and an increased range of mobility for the weak.