PlankMain Muscle: Abdominals Mechanics Type: Isolation Lay your stomach on the ground in a push-up position, with your elbows directly under your shoulders, your forearms and palms flat on the ground and your legs straight behind you. Keep your elbows at a 90-degree angle and raise your entire body off the ground, so that all your weight is resting on your toes and your forearms. Look straight, keep the back flat and contract the abs by pulling the belly in towards the spine. Hold for 30 seconds to a minute and lower the body to the ground. Focus on proper breathing and do not hold your breath.