Did your doctor actually say you're fine, as in "there's nothing wrong with you at all"?

Or did he actually say, "I've checked out your symptoms and good news- you don't have ALS or some other fatal, progressive neuromuscular disease. I have no treatment to offer you, this is just something you have to live with by avoiding the precipitating activities"?

Do you actually race in formal bike races? Or is your desire to be able to chase down stop signs with your friends?

Some people are pure sprinters and can't realistically perform well at endurance events. Maybe you're one of those types who'd shine at the track doing 3 min long races.