Core strength

The last days I learned a lot about the core-strength muscles. Especially if you are doing the repetitions too fast or with the wrong breathing or posture, it doesn't help anything. So here are some hints:

1. breath in by expanding the longues to the side! No "stomach breathing".

2 breathing out by pushing the belly button in and to connect the abdominal muscles.

3. Do every excercise very slowly to get the muscles working! The muscles used to give you a good posture are more static than dynamic.

On About.com there is a pretty good list of core-muscles:

Transverse Abdominis (TVA)-The deepest of the abdominal muscles, this lies under the obliques (muscles of your waist). It acts like a weight belt, wrapping around your spine for protection and stability.Target Exercise: Plank
External Obliques-These muscles are on the side and front of the abdomen, around your waist.Target Exercise: Arm Sweep
Internal Obliques-These muscles lie under the external obliques, running in the opposite direction.Target Exercise: Crossover Crunch
Rectus Abdominis-The Rectus Abdominis is a long muscle that extends along the front of the abdomen. This is the 'six-pack' part of the abs that becomes visible with reduced body fat. Target Exercise: Crunch
Erector Spinae -The erector spinae is actually a collection of three muscles along your neck to your lower back. Target Exercise: Back Extension

Use a gym ball!