Whats up. I just got back into riding after a long vacation from the sport. I also just stopped smoking so my lungs aren't up to the standards of what they should be. Anyways I have a habit of injuring myself so I want to train to cut back on the injuries especially since my right knee is still rebuilding itself from getting hit by a car in my bike about a year ago. Anyone know some exercises and stretches I should be doing? Or how long I want to spend a week riding? Any advice is welcomed. Thanks.

Assuming your otherwise healthy, have somewhat recently seen a Dr...

Get on the bike and ride gently. Keep it in a low gear so its easy to pedal and your legs spin (no hard pushing). Do this for a few weeks and don't worry about training or getting heart rate up to muc, instead get out there for at least 20min at a time and enjoy yourself. After doing this for a while you will get a better feel for your body again and then be a bit more disciplined after a month or two. Of course the approach won't be the fastest way to get in shape, but will likely be the way to do it without injury and something you can sustain while avoiding smoking.

Al

Go jogging and working out, screaming at the top of your lungs. Will help clean out the lungs and build up lung capacity :-D

EAT HEALTHY, and exercise on a regularly day basis

I pretty much second this response. You want to be healthy and fit, not just fit. By taking it easy you will reduce the chances of injury. An athlete with an injury is fit but not healthy.