Reverse Curl

• Lie on a workout bench and reach back to hold the underside of the bench. Bend your knees toward you while holding onto the bench, bringing your knees above your hips. Exhale and bring your legs back down onto the bench. This exercise strengthens your lower abdominal muscles.
  
  

Bicyle Kick

• Lie down. Bend your knees up at a 90 degree angle. Move your legs in a peddling motion to simulate peddling a bicycle. Put your hands behind your head and move your armpit toward the opposite knee as it peddles up. Continue this motion as you peddle. This exercise will keep your obliques and rectus abdominis in shape.
  
  

Crunch Twist

• Lie down. Put your hands behind your head and cross your fingers to lock them together. Bend your knees up and place your feet on the floor. Reach up with your left shoulder toward your right knee. Make sure you aren't lifting with your neck or head. Bring your shoulder back down and do the same movement with your right shoulder and left knee. This exercise will work the same muscles as the bicycle kick.
  
  

Situp

• Lie back with your knees bent up and your feet on the floor. Put your hands behind your ears. Lift your upper body up toward your knees. Lift with your chest and torso and not with your head, neck or arms. This exercise works your abdominal muscles.
  
  

Stomach Flex

• Sit on your chair with your back straight and your feet flat on the floor. This exercise can be done when sitting on a bench or at work behind your desk. Take a deep breath and flex your stomach muscles. Hold your muscles in a flexed position and count to three. Exhale and repeat. This works your abdominal muscles.