Next Friday will be 2 years since I quit smoking I still huff and puff ,especially riding up hill but it has gotten progressively better as time goes on. As for the pain you talked about I guess it depends on what kind of pain I know that when I first started to ride again it was a bit painful when it came to hills and of course I had to work my way up on distances and still sometimes experience a little pain when ridding up hill. I do not have any pain when I am done with the ride or the next day' I would say that if you are experiencing a lot of pain you may want to visit your friendly neighborhood doc and see whats up you may be trying to take on to much at once. The Pain no gain theory is a myth it shouldn't hurt a lot to exercise. Good Luck!