I had an MRI done on my knee last night. Since I had an impact 9 months ago I've had three incidents of varying intensities that sparked up a plague of swelling. It comes and goes when i play soccer with a knee brace. Long story short, I can ride a bike without pain and without generating any swelling. I am trying to prep for my soccer season... I am riding a stationary bike like a mad man. I can get my heart rate up and work for 40 minutes to an hour. However, I can never get that burning feeling in my lungs like I get when I run hill sprints or play soccer. My questions are 1. Can you work your lungs on a stationary bike? 2. If your not out of breath, are you improving your aerobic cardio? Or are you just building up your anaerobic endurance, strengthening your legs and burning fat? My goals are to lose another 16 pounds...(ive lost 9 so far). But more importantly improve my cardio for the season (which has always been lackluster). Thanks for advice.