While the barbell curl is another classic arm exercise, most people don’t know this game-changing tip of simply keeping your shoulders back. In fact, when performing all biceps movements, you want your shoulder blades back and retracted, as if you were pulling them toward the ground.
Doing so helps isolate the biceps and keeps all of the motion at the elbow joint. This keeps your front delts, back, and chest from unintentionally assisting in the exercise. After all, the goal is to place the stress from the barbell curl primarily on the biceps, not the rest of your body.