Abdominal Muscles

The abdominals are comprised of 4 muscle groups. 
1.  rectus abdominis
2.  external obliques
3.  internal obliques
4.  transverse abdominis

Your abdoninal muscles work to rotate and flex your torso.  They are also stabilizers of your spine. 

You should do abdominal exercises 3 times a week to keep these muscles in great shape.  When doing your abdominal exercises, be sure to do them slowly and feel the contraction with every lift.