First off,
http://www.usacycling.org/ for a license (link is on the sidebar)
Originally Posted by IndustriaL
xsdq how do i get a USCF license thingy I want to do that, and btw most bikers ride for the cardio and what better way to do cardio then racing
When you're below a certain heartrate, your muscles can receive their energy from chemical reactions involving the oxygen you get from your lungs, as well as carbohydrates or some other form of long-term energy store. This is aerobic exercise. This is why you can walk at a constant pace for a really long time.
Above a certain heartrate (what's called the lactate threshold or anaerobic threshold), your body can no longer process the oxygen fast enough to provide energy for your muscles. As a result, your body starts to use short-term energy stores without the need for oxygen. This is anaerobic exercise. Your body can produce a lot more power in anaerobic mode, but only for a short period of time. This is why after sprinting (on foot) at full speed for a short time, there comes a point where you slow down regardless of whether you want to or not. A product of the energy-producing reaction during anaerobic exercise is lactic acid, which is what causes your muscles to hurt after a period of exercise above the lactate threshold.
On the assumption that by "race" you mean "ride as fast as you possibly can," this would likely lead the rider out of the aerobic heartrate zone and into the anaerobic zone, which would hurt his training.