How to do it: Plank is an isometric (static) exercise where the rule is to hold your body correctly. Follow the example above: keep your back and legs straight without sagging or arching.
Results: If done correctly, the exercise works the abs, back, buttocks, legs, and arms. It also improves posture and general muscle tone.
How to do it: The initial position is a plank with straight arms. From there, lower yourself as far as you can. Make sure your back, pelvis, and legs form a straight line. Then slowly return to the initial position.
Results: Affects the chest, arms, and abdominal muscles.