Had the same concern 5 years ago. The answer is to go slow at first. Give time to heal up after surgery. But I have worked the abdominal area hard for 5 years, three times a week. Held a dumbbell out arms length while sitting down and swinging it left and right, up and down, and feel the strain and pain. The result has been hard flat stomach muscles and no tightening around the stoma. My worry has always been the surgical staples holding things together inside ever since I saw an x-ray of myself once... What are those little shiny things in the shape of fingernail clippings? But all has gone well, no problem. In this regard, I keep aware of the difference between sore muscles and possible internal injury regarding staples. Because of that concern, I have never done a lot of hard stretching such as deadlifts. That seemed to be more of a risk internally, but it may not be. I have been jogging consistently... 2 or 3 miles since 1996, again no problems. But jogging is getting harder to do, feet and knees getting old, lifting getting easier with age however. I am 74 years old and feel great, hard stomach... If you are younger, more power to you.