Cable concentration extension (on knee)

Sit on a bench or chair with your knees bent and feet flat on the ground. Hold the cable handle with your right hand and place your elbow on the inside of your right knee. Extend your arm fully, keeping your elbow stationary and close to your knee. Pause for a moment at the top, then slowly lower your arm back to the starting position. Repeat for the desired number of repetitions, then switch sides.