The purpose of this study is to compare the College Park Sidekicks to conventional stubby prosthetics to investigate their effects on bilateral above-knee-amputee gait velocity, exertion, and balance. The investigators aim to demonstrate that: (i) greater balance will be observed and reported on a level and gravel surface with the Sidekicks; (ii) time to complete the 10-meter walk test will be decreased wearing Sidekicks compared to the conventional stubby prosthesis; and (iii) subjects will report feeling less exerted with the sidekicks.