5. Woodchop

Instructions: Add some weight (start with 10-12kg) to a cable machine and grasp the handle attachment at shoulder height with your left hand. Square yourself to the machine and take a few steps to the right (away from the machine) until there is sufficient tension. Stand with your feet shoulder-width apart, bring your right arm across your body, and clasp your hands together while holding the handle. Keeping your arms straight and at shoulder height, use your abs to bring your arms across your body, as though you were making a wood-chopping motion. Then return them back to the starting position. Do 10 reps on each side for an excellent core workout.