An apparatus suitable for imitating one or more muscle members of a human user during physical therapy, wherein the apparatus is configured to be used in conjunction with the human user having a waist and a leg having a knee. The apparatus includes an adjustable waist belt configured to be secured around the human user's waist and a lower leg support configured to encircle the human user's leg in a vicinity of the knee. The apparatus further includes an elastic member configured to provide an adjustable tensile resistance between the waist belt and the lower leg support.