McKibben artificial muscles are pneumatic linear actuators with high strength-to-weight ratio and natural compliance. The actuator consists of an elastic cylindrical tube within an inelastic braided shell. With a sufficiently shallow braid angle, increasing internal pressure causes the muscle to expand radially and contract longitudinally providing a large actuation force. When McKibben actuators attach to an inertial load, however, PID position control cannot provide accurate tracking due to excessive vibration. Based on a third-order system model, two adaptive position controllers are developed, proven stable using Lyapunov Theory, and tested experimentally. First, adaptive control with a PID pressure loop yields acceptable sine wave tracking up to 3 Hz. Second, backstepping compensation for the pressure dynamics ensures accurate tracking of a 4 Hz sine wave with increased amplitude.