Getting in the Best Shape Possible Before Tummy Tuck With a Diastasis Recti?

I would continue with your fitness programs. Even if the diastasis gets worse, it will not be more difficult for your surgeon to repair. Keeping your weight down is the best thing you can do to have a repair that lasts. All the best. 

Hi

It is great to know that you are committed to getting the best result. Well done,I am certain you will not be disappointed after your TT. Keeping fit by doing core exercises helps you to attain your ideal body weight, lose intra abdominal fat and improve your body contour by loosing sub cutaneous fat ( fat under the skin). By increasing strength of core muscles you will increase the stability of your spine, improve posture and increase the blood flow and circulation to the area which is important when it comes to wound healing after your TT. When you have set up a great foundation your Plastic Surgeon can then get rid of excess skin, tighten the rectus separation and give you the pleasing contour you wish for. 

Since you have a structural separation of your rectus it is hard to imagine that strengthening your core would correct it. But your core muscles are very complex and they interact with one another in a very complex manner. You should consult with a physio who specialises in treating back injuries as they will know if it is possible. Physio for a lower back injury involves a LOT of core exercises. And I would not recommend doing core exercises unsupervised or without professional guidance.

Hope this helps