Grab a barbell with an overhand grip that's just beyond shoulder-width and hold it at arm's length. Stand with your feet shoulder-width apart and knees slightly bent. Bend at the hips, lowering your torso about 45 degrees, and let the bar hang straight down from your shoulders. Pull the bar up to your torso, pause, then slowly lower it. The same holds true here in terms of muscle involvement for both the pronated and supinated versions of the row.