Lie faceup on the floor with your knees bent, feet flat, and fingertips on your head behind your ears (a). Brace your core and raise your upper body until you're in a sitting position (b). Slowly lower back to the starting position. That's one rep.
Target: obliques, abs, forearms Keeping shoulders level, twist midsection to lower left hip toward floor; touch floor if possible. Return to plank and then lower right hip to floor. Do 20 reps, alternating sides. Do 4 sets.