There are 4 large systems, your training should include cycling.

1. Aerobic Conditioning
2. Slow-contraction muscle endurance
3. On lactic acid buffer
4. For fast muscle fibers

1. Aerobic happens between 70-80% of your maximum heart rate. Your body adapts to training in this area by increasing the volume of the lungs, and your muscles more efficient at using oxygen. This is achieved by a process called capillarization, which means that the number of capillaries increased in a muscle, which means that the muscle can be more oxygen and work at a higher rate of use without anaerobic means.

2. In slow-twitch muscle endurance is formed between 65-80% of your maximum heart rate. That's where most of your training should Cycling. In the area of the body to recruit more efficiently (with) slow fibers. Your body will also begin to develop more slow-twitch fibers, which means that you are your legs slowly always means more muscle. More than slow fibers means your leg muscles to spread the load exerted on her work and for longer periods.

3. Buffering lactic acid formed 80-90% of your maximum heart rate. About 1/5th of your total cycling training should be done in this area. The best way to make your system of lactic acid to 2 twenty minute train intervals, in the area, but this type of training is extremely difficult (and annoying if done on a turbo). Your body will adapt by producing less lactic acid, the more efficient in getting rid of him, and learn to use it as an energy source.

4. Fast-twitch muscle is formed between 90-100% of maximum heart rate. The minority of the training should be your bike in this heart rate zone. The best way to keep your muscles fast is interval training. The intervals must be extremely short (less than a minute), but with plenty of recovery between (3-5 minutes or as long as you want). Your body will adapt this training through more efficient recruitment of muscle fibers, and the development of more fast fibers. These are the fibers give that your legs muscular appearance (as Chris Hoy sprint test, they have the legs-trunk tree).
Your cycling training should be structured in such way, so you have your muscles enough time to recover and be structured, and to get the best result it can be a hard work