Disclosed power machines (100; 200; 300; 400; 500) include a lift arm structure (230; 330; 430) having a first arm (234; 334; 434) pivotally mounted to a frame and a second arm (236; 336; 436), coupled to an implement interface (270; 370; 470), configured to telescopically extend from and retract into the first arm. A control system (160; 260; 360; 460) controls a first actuator (238; 335; 435) to raise and lower the first arm, and controls a second actuator (239;) to extend and retract the second arm relative to the first arm. The control system is configured to control the first and second actuators to implement a lift operation, responsive to an operator input. During the lift operation, the first actuator raises the first arm and the second actuator extends and retracts the second arm to maintain a substantially linear path (339; 439), such as a vertical path, of the implement interface or an implement attached to the implement interface.