While crunches are a great abdominal workout, the plank is a contender for the best total ab and core exercise. Vary your plank style to increase intensity, avoid boredom and to focus on multiple parts of your abs and core. As if you needed another benefit, you'll get a killer upper body workout from the plank as well.
The Proper Plank
The plank is an extremely easy exercise. Think of a push up position. The top of the push up is the plank. Alternatively, you can rest down on your elbows, rather than your hands, until you are strong enough to complete the exercise on your hands only. The trick is to keep your entire body in line--from your head to your hips to your toes, your body should be in one straight line. Check your plank in the mirror to be sure that your backside is lowered in that straight line. Try to check it in the mirror the first few times that you perform the plank to create muscle memory.
Get in plank position and hold for 30 seconds. To rest, drop knees to the floor and scrunch back, so your backside rests close to your feet, hands on the floor, arms outstretched in front of you. Stretch back for 20 seconds, then return to the plank for 45 seconds. Repeat the stretch, then, on the third plank, hold for 1 minute or as long as you can.
As you get stronger, complete the plank, but alternate lifting each foot behind you, and hold each lift for 10 seconds. On a different set, alternate lifting each hand, arm outstretched in front of you for the 30 second hold.
Add a more intense shoulder workout and some instability to the exercise by alternating hand and elbow position. Begin in the standard plank on your hands. Drop down to your right elbow with your left hand still on the ground. Then drop to your left elbow. Rise up to your right hand then left hand. Repeat the drops, but begin by dropping to your left elbow first. Continue alternating hands and elbows for 30 seconds. Rest and repeat twice.
Lower Body Ab Crunch
Rest in a plank position, with your toes on a towel on a hard wood or tile floor. Slowly pull knees in together with legs on the towel. Feel your abs contract as you pull your legs in, completing 8-10 reps. Rest, then repeat two more sets. If you can't complete those, try putting your toes on two separate towels, and pulling in the right knee, then alternating left. That's one rep. Work slowly to focus on using the abs--not momentum--to bring knees in. Complete 8-10 reps before resting.
Turn your plank on its side, resting on your feet, one in front of the other. Lift one arm toward the ceiling and hold for 20-30 seconds. Push hips toward the ceiling to engage the obliques. You should feel the contraction on the side that is closest to the floor. Repeat on the other side.
Keep working harder to make the plank work better for you. Try to do each of these exercises as many times as you can working up to higher reps and increased strength.