Having had two babies, one by c-section, in my 20's and 30's, I know my abs aren't nearly as strong as they used to be - despite working out deperately to get that flat stomach back after baby #1 (the c-section). Once muscles have been stretched that far or especially if they've been cut, they are never quite the same, even with regular exercise. If you don't get regular exercise,and add in the effects of time, gravity, possibly gaining and losing that same 10 or 20 lbs over and over, it's no wonder by mid 30's to mid 40's women's abs may be weaker than desired.

I think firmer abs would tend to support the upper torso more and promote better posture, maybe take some strain off the pecs. Also, it seems as though better breathing would be established as you more naturally breathe from your abdomen when your posture is correct. And by providing better support for the structures and organs of the thoracic cavity from below, firm abs along with strong side and back muscles might help reduce some brachial plexus distress due to weight and gravitational pull on the chest.

Anyway, it's definitely worth a try to see if I can cope working on building these muscles, the injured ones are a no-go for sure!