Drag Curls
Thankfully, this exercise does not require inappropriate gym attire. "Drag" refers the bar lightly touching the torso during execution. Drag curls are among the most efficient (and overlooked) biceps-building exercises. They effectively overload the biceps muscles by combining a contracted starting position with a controlled motion that contracts them even further.
Using a straight bar, position both your fingers and thumbs on the underside of the bar (see photo at left). During the movement, keep your shoulders lowered and immobile and your wrists straight. Avoid the temptation to roll your wrists up.
Slowly raise the weight, lightly dragging the bar up your torso. Keep your shoulders down and your elbows back. The range on a drag curl is short, from the navel to the nipple, with the ending position at or below the nipple level. Perform 8 - 12 repetitions using slow, controlled movements.