Grasp handle (palm up) from top pulley. Sit in good body alignment (abs tight, chest up, back straight). Bend forward to position upper arm (triceps) against leg. Keep opposite arm stationary. In a controlled motion, keeping upper arm perpendicular to the floor, extend the arm down toward the floor. Contract triceps fully, without compromising form. While maintaining the controlled motion, return arm to starting position. Do not allow muscles to relax before next repetition.
Here are a few suggested alternative exercises:Ball Band French CurlBall Band Triceps KickBackBand KickBacksBand Overhead ExtensionBand Tricep ExtensionClose Grip Bench Press - BarbellClose Grip Dumbbell PressDecline Dumbbell Close GripDips - MachineDumbbell Lying ExtensionTricep Extension - Hammer Strength