I'm not talking heavy excercises here like squats, deadlifts or bridges, but what I need to do(and probably a lot of us) is to reactivate the deep abdominal muscles. Like this(taken from John stone fitness forum):
"TA/MF Activation
1. Lie on your back with your legs/hips bent at a 45 degree
angle. You should have a natural curve of the spine.
2. Place a finger on each hipbone and move your finger in 1cm.
Press in firmly and this is where you will feel the contraction
the TA/MF.
3. To feel the contraction do several mild coughs or laugh and
feel the slight contraction. This is to give you an idea of the
actual muscles contracting and to try and differentiate
between the TA and the outer stomach muscles.
4.( Next contract your pelvic floor muscles by pretending you
need to go to toilet and you must stop yourself from
urinating.) Not a good thing to do for us
skip this one!
5. Now slightly suck in your belly button towards your spine and
you should feel the TA/MF contract.
6. Don't suck in you belly too much, it should be easy to feel
the contraction.
7. When you contract the TA the Rectus Abdominis should
remain relaxed.
8. Breath as naturally as possible through your nose.
You should practice holding the TA/MF contraction as long as you can while breathing normally and then while breathing deeply. Practice the contraction standing, lying on your stomach and walking.
The goal is to be able to automatically contract the TA and hold it while you walk, lift things, workout at the gym and run. It should be activating all the time during the day whenever movement is present and the lumbar spine needs to be supported.
One you can easily contract the TA/MF you can then progress though certain exercises that strengthen and improve the Central Nervous Systems coordination."
