Exercise execution guide
Stand in front of the cable machine, legs shoulder width apart, and grasp the straight bar with an underhand (supinated) grip and your hands about shoulder width apart.
Keeping your body fixed, elbow tucked in at your side, and eyes facing forward, slowly curl the weight up as far as possible without letting the elbow move forward excessively; only your forearms should be moving. Squeeze the biceps at the top of the movement, and then slowly lower the weight back to the starting position. Repeat for desired reps.