Rear ended by a car at 35mph. Two fractured vertebrae, elbow bones abraded on pavement, dislocated rib, major contusions. Committed myself to fullest possible recovery while in the emergency room. Didn't ride for 6 months. Lost weight, mostly muscle. Cardio fitness diminished significantly.
First ride was 4 miles. Rode when I felt that I could, for as far as I thought prudent. Slowly built base. Added regular and reverse crunches to my upper body weight training regimen. It's been nine months now and I'm still recovering.