The breath alone is a very powerful tool.
You do not have to be fit, you do not have to be pain-free you can be young or old, you can be anywhere to do it and in any shape or form.
In pilates the breathe is a fundamental concept. It is used to trigger deep core strength and tone these muscles. Critical for balance.
So, in order to strengthen your deep core, on each exhalation , imagine your deep core. Imagine a thick belt that begins at your low back and wraps around the midline like a thick belt. This muscle is a very important stabilizer. It stabilizes the body and helps with balance and overall strength. It does not create movement, it just stabilizes. This particular muscle is called the transverse abdominus.
Imagine tightening it and allowing it to wrap itself tighter around the midline like a belt, a belt that is 4-6 inches wide. Upon doing so, the front of the belly flattens, the side body narrows ever so slightly and we feel a gentle tightening in the low back.
Inhale gently, and then exhale. Inhale gently and repeat..
It is very important to relax. It doesn't matter if its 100% perfect. I like to say that we are tending towards the idea of the movement but it's important to relax and enjoy it all. Don't worry about perfection, otherwise it'll be a chore and no fun at all.
As you exercise try to exhale using this idea. Try to help drive the movement with the strength you feel deep inside. You can practice in the car, you can practice as you walk. The breathe alone will create tone and strength.