Do the Plank!

1) Now, lie face down on a mat (or just your carpet) resting on your forearms, palms flat on the floor with your elbows directly beneath your shoulders.

2) Next, push off the floor, raising onto your toes, resting on your elbows. Keep your back flat, in a straight line from your head to your heels. Tilt your pelvis and engage (contract) your abdominal muscles so that your buttox is neither sticking up into the air nor sagging causing a sway in your back.  Keep your gaze directly on the floor.

3) Hold for 20 to 60 seconds.  As you begin to feel your muscles shake and your mind begins to cry out, “I can’t do this!” stay strong.

4) Repeat 3-5 times.

Source: http://csfaithandfood.com/fitness-friday/do-the-plank/