Pulling your abdominal muscles in and holding them interferes with natural breathing. This could lead to weakened diaphragm muscles and shallow breathing. Holding your abdomen in for long periods of time will lead to your body getting less oxygen. Less oxygen means feeling tired, less concentration and a lower metabolism. Research has linked poor breathing patterns with lower back pain (although like the chicken and egg, they are not yet sure which came first!). Holding muscles for long periods of time will actually weaken them. Muscles are designed to contract and relax.
One thing that is for sure; if you are holding your abdomen in, you are only using some of your core muscles. Our core is a system which stabilises us and transfers force safely through the body. This is complex system involving many muscles.
One of the simplest ways to engage more core muscles is to ‘lift’ up through the centre of the body. Start with your pelvic floor muscles between your legs – tighten them and gently ‘lift up’ into the body. (And before you ask, YES men do have these as well!) As you lift you should feel a response, a tightening, low down in your abdomen – your pelvic floor is helping to activate your abdominal muscles. Imagine pulling this tightening up through the centre of your body – behind your belly button and through the centre of the ribcage until it lifts the top of your chest. That’s most of your core now activated!
This method will activate far more core muscles than just holding in your stomach. Using your pelvic floor will help with stress incontinence and also improve your sex life.