Old exercise: Plank
Upgrade: Around-the-world plank
How to do it: Place both feet on a bench, and assume a pushup position. Brace your core. Then, without dropping your hips or moving your feet, make a full revolution around the bench by "walking" your hands all the way around it. Do 4 revolutions, resting 60 seconds in between revolutions.
Benefit: The stabilizing muscles in your abs, upper and lower back, and shoulders work harder than they would in a traditional plank.
Old exercise: Crunch
Upgrade: Anti-rotation crunch
How to do it: Attach a rope to the low pulley of a cable station and lie on your back alongside the stack. With both hands, hold the rope in front of your chest. Perform a crunch, arms locked, and don't let your torso rotate (even though the cable pulls you sideways). Pause, and return to the starting position. Do 15 reps, switch sides, and repeat. That's 1 set. Do another set of 12, and a final set of 10. Rest 45 seconds between sets.
Benefit: You're boosting the intensity and efficiency of a traditional crunch, and your abs have to work harder to prevent rotation.
Old exercise: Side plank
Upgrade: Side plank with low-cable row
How to do it: Attach a handle to the low pulley of a cable station and lie on your side, facing the stack. Grab the handle with your top hand. Raise up into a side plank: knees straight, upper body propped on your elbow and forearm. Pull the handle to your rib cage; keep your hips pushed up and forward. Slowly extend your arm. Do 10 to 15 reps, switch sides, and repeat. Do 2 more sets, resting 60 seconds between sets.
Benefit: By engaging your lats, the fan-shaped muscles in your back, you increase torso stability and muscle endurance.