This is biceps strength building exercise. You need a cable pull machine to do this exercise.

1. Take a straight bar or  an E-Z bar that is attached to a low pulley. Use both your hands with your palms facing up. Grip the bar at shoulder width.
2. Set up an exercise mat; lie flat on top of it. Set your foot flat against the pulley system frame with your legs stretched.
3. Extend your arms but keep you elbows close to your torso. Bend your arms a little to assume the initial position.
4. Keep your upper arm in position with your elbows remain close to your torso. Pull the bar gently towards your chest while you exhale. Feel the contraction of your biceps.
5. While inhaling slowly return to the initial position.
6. Do for the suggested no of reps.

Video Demo on How to do Lying Cable Curl

Video Demo 2