Hold a rope handle attached to a low cable with one hand and the palm facing inward. Curl the arm up as far as possible, and lower under control. The neutral grip can be maintained throughout, or the hand can be slightly supinated during the curl.
 
Purpose
The cable curl generally keeps a more continuous level of tension on the biceps than a dumbbell or barbell curl and is a good general bicep strength or hypertrophy choice. The rope handle increases the grip work and creates a neutral grip for more brachioradialis and brachialis work, or allows a partial supinating motion to change the emphasis through the movement. It also tends to place less strain on the elbows by allowing the arms to move more freely. Training a single arm at a time helps develop and preserve symmetry side to side.
 
Programming
Generally 8-20 reps are appropriate, and more can be appropriate for forearm emphasis.