Plank on knees - version 2

Lie down on a mat on your front.
Lift your chest up off the floor using your forearms.
Lift your hips up, keeping your knees on the floor.
You should have a straight line from your knees to your shoulders.
Keep your shoulders strong and do not sink down at the hips or the chest.
Hold this position.
Relax and return to the starting position.