Transverse Abdominal Muscles

• Begin by working on your transverse abdominal muscles. These are the deepest abdominal muscles, and they provide both thoracic and pelvic stability. They run horizontally, like a weight belt.
  
  Try the plank exercise for a demanding transverse workout. Get down in a push-up position. Lower yourself onto your elbows, shoulder-width apart. From head to heel, your body should remain in a straight line, or plank. Hold this position for 30 to 90 seconds, depending on your fitness level. This is one set. Do three sets with a 20-second break in between.
  
  Use the vacuum cleaner exercise to further strengthen these muscles. Begin by fully exhaling. Expand your chest while at the same time drawing your stomach in as far as possible and holding it for five to 10 seconds. Attempt to touch your navel to your spine. This exercise can be done while standing, kneeling, lying or sitting. Do three sets of 10 to 20 repetitions, with a one-minute break between.
  
  

Oblique Muscles

• Tighten your internal and external oblique muscles. The oblique muscles work together to lend torsional, or twisting, movement to the body. The internal muscles are integral to exhalation while the external muscles are the primary means by which the chest is flexed downward or forward. The internal muscles are deeper than the external muscles, though neither are as close to the spine as the transverse muscles.
  
  Continue with oblique crunches. Lie down on the mat with your knees bent and feet on the floor, then let your legs drop to one side. Place your hands behind your head without clasping them and let your elbows fall to the side. Lift your shoulders off the ground slightly, hold for one second and release. Move slowly and do three sets of 20 on each side, with a 30- to 60-second break in between.
  
  

Rectus Abdominal Muscles

• Focus on the rectus abdominal muscles--or washboard abs--if you still have the strength. These muscles are superficial, meaning they are farthest from the spine and play a role in posture as well as providing a protective wall for internal organs.
  
  Start by lying on your back and doing vertical crunches. Lift your legs vertically with your knees slightly bent and crossed at the ankles. Place your hands behind your head without interlocking your fingers. With your elbows touching the floor, lift your shoulders off the floor as if trying to bring your chin to your toes. Do 15 to 30 repetitions slowly and three to four sets. Take a one-minute break in between.