Level One: raised mountain climber

For a standard mountain climber, start in a pushup position with hands under shoulders and core tight, the body should form a straight line from head to ankles.
Raise your left foot off the floor and raise the knee as close to the chest as possible, touch your toes to the ground – extend your left leg back to starting position and simultaneously drive your right leg towards your chest and your toes to the ground.

Level Two: Mountain climber

Level Three: Mountain climber on a Swiss ball

CAUTION:

Don’t bounce up and down. Don’t come too far back with your hips – be sure to keep the plank position.