Forget the crunches! If you want rock solid abdominals then you should be all about the plank. As far as exercises go, you get the best bang for your ab-rocking buck with planks because this single hold is all about building “isometric strength”, which refers to strength building exercises where you hold a move by contracting your muscles yet don’t actually move a muscle.
The plank can also be considered an exercise that engages multiple muscles—including the shoulders, triceps, biceps, forearms, back, hammies, and even the glutes—if you choose to mix these plank variations into your workout routine…
Plank with Straight Arms
This straight-arm plank holds your body in the up position of a pushup. So if you’ve ever done a pushup, you’re already familiar with what it feels like to hold your body in the top pushup position.
For those who aren’t, you can start lying face down with arms bent and hands at shoulder width. Legs should be extended with toes at hip width. Push up simultaneously through the hands and toes as you contract the abs and legs. Keep your body (butt down) and straight as you can.