Still doing crunches in pursuit of six-pack abs? Trade in your crunch routine for the plank instead. Not only is it a more effective abdominal exercise, it’s also better for your back. Research suggests that crunches and sit-ups put a hefty load of pressure on the spine, which could put you at risk of a herniated disc. Start on the floor, on your knees and forearms. Clasp your hands in front of you. Your elbows should be directly below your shoulders. Extend your legs behind you and raise your body so that you’re supported by the balls of your feet, which should be hip-distance apart. The position should look like you’re doing a push up from your forearms instead of your hands. Face the floor, and maintain a straight back. Be careful not to arch your back or stick your butt in the air. Hold this position for as long as you can, eventually working up to 60 seconds as you get stronger.