A plank exercise is an isometric exercise, which is when you are pushing your muscles against something else. Normally, this involves doing an exercise on the ground where you are using your arm to hold yourself up from the floor for a certain length of time. The challenge behind a plank exercise is keeping the position for as long as you can. The most common plank exercise is the pushup hold. The only difference is that you are not pushing up and down off the ground. You push up once and then hold your body in the air. This puts pressure on your toes, elbows and forearms. The longer you hold the bigger the burn you will get, which means those muscles are strengthening through endurance.
Plank exercises are most commonly used in yoga. Pretty much all yoga positions involve stretching your body to an awkward position and then holding that position for as long as you can. Regardless of what type of plank exercise you perform, you should first make sure you have a soft surface to do it on. That way you will be able to do a plank hold properly on the ground. One of the most common plank holds done in the military is the side plank. This is where you lay down on your side and hold yourself up by your forearm and elbow. Make sure you keep a 90 degree able in your arm, so that your forearm is not squeezing up against your bicep. This is a great exercise that works the oblique muscles, which are the muscles on the sides of your abdominals. The oblique muscles often get overlooked when people train their bodies. The same goes for the glute muscles as well. However, they are all very important to work out if you want a balanced looking figure.