A static exercise for the abs and spinal extensors. It also back, arms and glutes.
Get into a prone position on the floor.
Bend your arms.
For a more difficult variation – straighten your arms with your palms placed on the floor.
As you inhale, lift your torso parallel to the floor.
Only your toes and forearms should touch the floor.
Keep your body straight. Don't arch your back, keep the neck straight, tuck the abdomen.
Hold your breathe, then breathing out slowly, hold this position as long as possible.
Slowly get down on the floor.
Take a break and do another rep.
Avoid arching your torso and don't tense your shoulders or raise them to your ears.
You can extend your hands forward in turns raising them sideways then out to the front.
Another way to increase difficulty is to do the plank with a BOSU ball.