Doing abs will not make your tummy "flat"! There is a layer of fat between the muscle and the skin and when this layer is excessive the only way to flatten the belly is to lose excess fat .

The muscles that we commonly call "abdominal" are actually the abdominal rectum ( Rectus Abdominis ), which runs from the pubis to the lower end of the sternum.

Exercising in the abdominals will shorten the Rectus Abdominis excessively, which will "pull down" the rib cage, the shoulders will tend to round, bringing the neck forward.

Strengthening and stability exercises ( Core Stability , in the sports field refers to a region of the body formed by two muscular systems, local musculature and global musculature) have been developed in response to a perception of poor muscular support.