There are many reasons for working out in a progressive, integrated fashion. One of the main reasons is due to the different muscle fiber types and their responses to resistance training. Muscle fiber types vary in their chemical and mechanical properties. They've been separated into two main categories: Type 1 and Type 2.
Type 1 muscle fibers or "slow twitch" are smaller stabilizing muscles. They produce less force and are slow to fatigue. These fibers are important for muscles producing long-term contractions needed for stabilizations and postural control.
Type 2 muscle fibers or "fast twitch" are larger short-term contracting muscles. The produce more force and power and are quick to fatigue. These fibers are important for producing movements like sprinting.
All muscles have a combination of slow and fast twitch muscle fibers that will vary depending on the function of the muscle. It's been shown that the muscles on the shin are approximately 73% slow twitch while part of the calf has approximately 49% fast twitch.
In order to have successful, efficient results, it requires a varied and integrated program that encompasses all aspects of training: flexibility, stabilization, balance, strength and power. If all of these components are addressed, your body will function at an optimum level of performance, the risk of injury is decreased and results will be quick to happen.