Dr. Laskowski: The biceps curl is an exercise you can do with a weight machine to work the muscle in the front of the upper arm. As the name implies, the biceps curl helps you build strength in the biceps muscle, here in your upper arm. If you use a cable system, you can also work your core muscles and improve your stability.
Nicole Campbell: To do a bicep curl with a weight machine, start by grasping the bar with your palms facing upward. Slowly curl the weight up by bending your elbows, and stop when your elbows are bent to 90 degrees. Then slowly lower the weight back to the starting position. You'll feel tension in the muscles in the front of your upper arm.
When you're doing biceps curls, be careful to keep your wrists straight and rigid. If you flex your wrists as you bend your elbows, you won't target your biceps effectively and you may hurt your elbows.
For most people, one set of 12 to 15 repetitions is adequate.
Remember, for best results, keep your wrists straight and rigid during the exercise. Also keep your movements smooth and controlled.