How do you resume activity? Slowly.

I had a nephrectomy two years ago (the incision is similar to that for an abdominal hysterectomy) and couldn't do much more than walking and tai chi for the first 4 weeks. I don't run, but even a short jog to get across a busy street was very uncomfortable. Simple activities like push ups were impossible. I did finally get back on the bike at around 5 weeks post-surgery, and even did a 100k at the 10 week mark. You will slowly regain your strength and stamina, and abdominal muscle, but expect to take it easy for the first few weeks and definitely don't try to overdo it (and develop a hernia like I did).

Good luck.