Keep your back straight and legs straight. If you cannot manage to lift your legs straight, grab hold of your calves instead of your ankles.
Point your toes. Tense your abdominals and draw your belly button back towards your spine.
Muscles required: trapezius, gastrocnemii, quadriceps, lateral dorsals, buttocks.
Sit with your back straight and bend your knees. Place your hands on your thighs, just behind your knees. Part your knees a little. Your back and neck should be in line.
Grab hold of your ankles, put your heels together, with your knees apart. Slowly lean your chest back, but keep your back straight. Tense your abdominals as much as possible.
Straighten your legs:
Slowly start to open out your legs, upwards, then draw them apart. Your toes should be pointed. Return to the starting position as you breathe in. Do not place your feet on the floor.