This is an exercise movement for the triceps. Primary muscles used in this exercise are the triceps. Secondary muscles used in this exercise are the forearms and deltoids.
To perform cable rope extensions you will obviously need to use a rope attachment on the cable machine. Standing with your back facing the machine grab the rope above your head. Lean forward at the waist, your back should be straight at a 45 degree angle. Now forcefully pull the rope forward extending at the elbows until your arms are straight. Slowly control the weight back to the starting position. Repeat the process.