RoboJoey is a vertically constrained monopod hopper designed for 24-775: Robot Design and Experimentation at Carnegie Mellon University. The proposed research aims to observe the relationship between tendon length and energy efficiency in legged robots. The robot is designed with a modular tendon mechanism which allows for adjustment of tendon length. The robot will consecutively jump to a specified height with the use of inverse dynamics and kinematics. Energy efficiency of the robot will be recorded for different tendon lengths and configurations.