Find a weight bench, or if you're outside, use a park bench. Place your hands on the bench and your feet on the ground. Lower your chest to the bench and push back up.
Pushup with knees down
The more parallel your body is to the ground, the harder this exercise is. Beginners can start on their hands and knees; this position trains important shoulder stabilizers and lowers the stress on the lower back and the joints themselves, Suprak said.
Start in a plank position, or the "up" position of the pushup, with your body in a straight line and your hands just slightly more than shoulder-width apart. Tighten the abs as if bracing for a punch and slowly lower the chest toward the ground. Aiming at a target can help get the chest close to the floor, Olson said. Simply lay a water bottle or hand weight vertically on the ground. Slowly lower until the sternum touches the object. Keep the stomach off the mat and the back straight. Narrower hand placement benefits the triceps and the chest, Olson said.
Elevating the feet makes the pushup harder. Use a low bench or a stair, which is about 5 inches tall, Olson said.
Minus a limb
Using a single limb -- one hand or foot -- instead of two, can increase the difficulty. Ground your right foot, stack the left foot on top of the right and lower down. Or, keep both feet on the ground and just use one hand. Be cautious. "A one-handed type of pushup causes a tendency to rotate around the lumbar spine," Suprak said. "There's a torque causing rotation of the body, and you're trying to stabilize. That can cause increased stress in the discs between the vertebra, he said.
Medicine balls, stability balls, basketballs and BOSUs can all be used to decrease stability, working more muscles. Pausing at the beginning, end or middle of a movement will make it even harder. Some research shows unstable surfaces may increase the activation of the muscles that stabilize the shoulders, but studies are inconclusive.
Wobbly surfaces will, however, definitely increase trunk stabilization," Suprak said. And the chest can drop lower than normal if you're on three balls, so be cautious about going deeper, Olson said. "Basically, all your muscles are doing double duty; they're moving and stabilizing you, which can easily lead to injury."
Calderon, the pushup champ, sets up for medicine ball pushups by putting each hand on a ball. "Then it's one foot at a time until I'm stable," said Calderon, who is shooting for a new record: pushups using just two medicine balls.