Originally Posted by Crunkologist
I'm not worried, I was just wondering if this was how people get tired on bicycles. Whether they get winded, or their legs get sloppy tired.
You're going too hard for your level of conditioning. Back off on your exertion level and slow down some. If you are only able to do 5 to 10 miles, there's no sense in trying to set a speed record. Try maximizing the time you can ride, not the distance. I recommend you also get a heart rate monitor so you can better pace yourself and keep your heart rate around 80% of maximum. You'll get the most benefit from your workout and build cardiovascular conditioning more effectively.