One way to make pullups more challenging is to strap on a weight belt, run its chain through the center of a weight plate, and knock out reps with the weight dangling between your legs.
But if you cringe at the thought of an unforgiving chunk of iron swinging freely near your 21st digit, the arched-back pullup is a better alternative.
“This exercise involves both a vertical and horizontal pull from the upper body—most pulling moves involve only one or the other,” says Martin Rooney, founder of the Training for Warriors method. “It maximizes core and abdominal recruitment, so the arched-back pullup hits about as much total muscle as any lift.”
How to do it
Fix a V-grip handle on a pullup bar, and hang from it. Arch your back completely, and pull yourself up so your chest meets your hands at the top and your torso is almost parallel to the floor.