A prosthetic or orthotic device includes a body configured to support at least a portion of a human limb of a user wearing the prosthetic or orthotic device. The device can also include a shock absorption member coupled to the body. The shock absorption member includes one or more magnetorheological elastomer (MRE) springs disposed between a first portion of the body and a second portion of the body. The one or more MRE springs are selectively actuatable to vary a stiffness of the shock absorption member via the application of a magnetic flux, thereby adjusting a stiffness of the body of the prosthetic or orthotic device to a level corresponding to an activity level of the user.