the risk of injury comes with the game. You have to decide if it's worth it. There will always be crashes. The higher up you go, they're just faster crashes.
Couple of observations:
1)If it gets you off the couch, i bet eliminating the sedentary lifestyle risk factor more than offsets the risk;
2)I think the risk of serious injury or death is lower racing, than just ridingon open roads;
3) Your personal risk goes down with experience. When I did this in my 20's my first 2 seasons I had several crashes; most of which were either my fault, or could have at least have been avoided with better skills. Now older, and hopefully a little wiser, I've had one crash in 20 races, and it was pretty minor.