Try walking each day at a mall or around a store like Home Depot. I am about 9 weeks from open heart surgery and i try to walk 30 minutes each day. If I am too tired to do 30 minutes at one time, I do 15 and15. Slowly this walking is making a big difference. I would start rehab right away. It was strongly suggested I start rehab 4 weeks after surgery no matter how I was feeling.