Do 2 sets of each of the following exercises, 12 – 15 reps per set. Rest no more than 1 minute between sets. As you get stronger increase the number of sets but don’t do more than 20 reps per set. Again, if you feel the sets are too easy you’re probably not doing the exercises correctly.
The point of this free ab workout routine is to get a quick, intense ab workout that burns fat, strengthens your abs, and leaves you in a puddle of your own sweat. Have Fun!

Exercise 1: Bicycle Maneuver~The number 1 overall ab exercise.
Lie flat on the floor with your lower back pressed to the ground. Put your hands beside your head (NOT behind). Bring your knees up to a 45-degree angle and slowly begin “pedaling” as if you were riding a bicycle. Each time your bring one of your knees up touch it to the opposite elbow (left knee to right elbow, right knee to left elbow). A single rep is every time you’ve touched both knees to your elbows, so 30 “pedals” is actually 15 reps. Here is a picture showing correct form:

Exercise 2: Reverse Crunch~ One of the best exercises for lower ab development.
Lie flat on the floor with your lower back pressed to the ground. Put your hands beside your head or extend them out flat to your sides. Cross your feet at the ankles and lift your feet off the ground to the point where your knees create a 90-degree angle. Once in this position, press your lower back on the floor as you contract your abdominal muscles. Your hips will slightly rotate and your legs will reach towards the ceiling with each contraction. Exhale as you contract; inhale as you return to the starting position.

Exercise 3: The Plank ~The best core strength exercise.
This is one of the most effective “core strength” exercises you can do because it works all the torso muscles, including those in the lower back and abdominal region. In fact, to maintain this position you use just about all of your muscles. Here’s how it’s done: simply get into the normal pushup position and hold it (strictly) for 30 seconds. Keep your abs very tight and your body straight. It will seem easy at first but after a few 30-second reps you’ll definitely be feeling it. Just be sure to tilt your pelvis and contract your abdominals to prevent your butt from sticking up in the air. An easier version of this exercise (weight on your elbows) is shown in the photo below: