Barbell Curl

The barbell curl is the classic mass builder for the biceps and the standard everyone measures arm curls against. Holding a straight bar with an underhand grip, you bend at the elbows to raise it toward your shoulders while the rest of your body stays quiet, making the biceps the sole prime mover through a clean, direct arc. Because both hands share one bar, you can load it heavier than most curls and progress in tiny increments over time, which is exactly what steadily builds arm size and pulling strength. It's simple, effective, and hard to overthink. The one way it goes wrong is momentum: swinging the weight up or rounding and heaving with your back robs the biceps of the tension that grows them and can strain your lower back and wrists. Keep your elbows pinned to your sides, your torso still, and lower under control rather than dropping the bar. Do it strictly and it stays one of the most productive arm movements you can pick.