Strengthening the core muscles of the body is one of the principles of Pilates. Many books, fitness DVDs, and classes promote Pilates abs,  but these ab exercises aren’t unique to Pilates. Pilates abdominal muscles exercises are essentially any exercise that focuses on the deep abdominal muscles that stabilize the core of the body.

By contrast, variations on abdominal crunches and sit-ups work the rectus abdominus (the six-pack muscle tissue on the front of the abdomen). For a truly solid core, include both classic crunches and deep muscle or Pilates abs  exercises into your primary fitness workout plan.

Here’s a deep ab workout to try:

Start by lying on your back.
Pull your knees towards your chest and place your hands behind your head. Be sure not to lock your fingers or pull on your neck!
Bring your left elbow towards your right knee while extending your remaining leg straight out in front of you, parallel to the floor. Hold the position long enough to exhale, then repeat on the other side. Repeat five times on each side for a total of 10 crisscrosses.