The two most popular exercises in any gym are the bench press and the curl. When someone says, “Make a muscle,” you automatically flex your biceps. Developed biceps are a sure sign you’re working out regularly.

The curl has been the standard exercise for developing the biceps. Most trainees begin with the barbell curl, and they experience increased biceps strength and growth. As they continue, they usually come across a cambered bar, sometimes known as an EZ-curl bar, which is a barbell that has been bent so there are subtle changes in the angles where the hands hold the bar.

The angles can reduce stress on the wrists and forearms. Stress on the ligaments and cartilage in the wrist contributes to wrist pain during barbell curls. The forearm pain may be caused by tendonitis and by stress on connective tissue structure between the radius and ulna, the two long bones of the forearm.

Eventually, almost all trainees try the dumbbell curl. There are distinct advantages to the dumbbell curl, the most important being that you have the freedom to move your wrist to find positions that don’t cause pain in the forearm. Of course, if the dumbbell curl doesn’t cause pain, or as much pain, you can be more consistent with your biceps training, resulting in greater strength and muscle gains.

The technique of the dumbbell curl that has evolved is biomechanically correct. You hold the dumbbells with the palms of your hands facing your thighs. As your elbows begin to bend and the dumbbells start to clear your thighs, you should begin to turn your palms upward toward the ceiling. That turn, known as supination, should occur gradually. The biceps brachii bends your elbow and turns your palm upward. It also has an action on the shoulder that includes flexion (raising the arm straight up in front of the body), and it has an effect on overhead-pressing strength due to better shoulder stabilization.

That all seems simple enough, but there are two other areas of concern during the dumbbell curl. The first is the shoulder. When you have a rotator cuff injury—with or without instability—it’s very difficult to stabilize your shoulder, which makes the dumbbell curl difficult to perform. That’s obvious when you perform a strong, perfect dumbbell curl with one arm, and when you try the other arm, the shoulder dips to compensate for the injury. The elbow on that injured side is usually held a little closer to the body too. The heavier you go on the curls, the more pronounced that will be.

Once you address the shoulder problem and reduce the inflammation, perhaps with ice packs, and begin a strengthening program for your rotator cuff and shoulder blade, the injured shoulder will become stronger and will be able to support heavy dumbbell curls.

The second potential problem is the aggravation of low-back pain. You can do dumbbell curls with one dumbbell at a time or two at a time. Working both arms together places more weight in front, especially at the midrange point of the curl. That will cause your back muscles to fire more, and as the dumbbells become heavier, you lean back to some degree. The lighter the weight, the better the posture.

If you’re experiencing pain or discomfort while simultaneously curling two dumbbells, try going one arm at a time or alternating reps. There’s another advantage of the alternate style: You give the muscle a little longer time for recovery, and that will enable you to handle more weight. There are few trainees who don’t want to handle more weight.