Bring yourself to the ground in forearm plank position with your elbows directly under your shoulders and your legs extended directly behind you. You should have an unbroken line from your head to your toes. Keep your core braced and do not let your hips drop. Proceed to lift your left arm away from the floor and tuck in behind your back so it's resting at the base of your spine. This is the position you need to hold. Hold for the required time, keeping your core braced and a neutral spine throughout. Then proceed to swap arms and maintain the same position for the required time.