Dumbbell Concentration Curl

The concentration curl is a biceps isolation exercise in which the back of your upper arm rests against the inside of your thigh while you sit on a bench. That contact point is the exercise. With the elbow locked against the leg it becomes impossible to swing the torso or help with the shoulder, so the only way the dumbbell rises is by contracting the biceps, and the muscle is felt more clearly here than in almost any other curl. Expect the weights to be lighter than on a standing curl, which is the honest consequence of removing the cheating rather than a sign of weakness. Working one arm at a time lets you address strength differences between sides that a barbell curl hides completely. Straighten the arm fully at the bottom, because a large part of the stimulus lives in that stretched position.