First, lets start this post off with a little info about what a muscle fiber type is. Muscle fibers are divided into four catagories: Type I, Type IIa, Type IIx, and Type IIb. Type I fibers are your slow-twitch, oxidative fibers. That means these fibers are very good at aerobic activity. The Type II fibers are primarily fast – twitch fibers who function anaerobically. Here’s a chart:
So, back to the original question, does muscle fiber type effect your performance? Sort of. Most people are usually 55/35. That means they may be 55% Type II or 55% Type I. As you can see by the chart, people who are oriented more toward Type II will tend to be better at activities that require short bursts of energy, like powerlifters, strongman competitors, olympic lifters, and sprinters. On the flip side, people who are oriented towards Type I fibers tend to be better at activities that are aerobic in nature like marathon runners. That being said, it doesn’t mean that you can’t train an elite powerlifter to run a marathon. You absolutly can. It just means they be winning the Boston Marathon anytime soon.
For field athletes (like soccer and football) it really doesn’t effect whether you’ll be good or not as much as it efftects how you play the game. Take for example Payton Manning vs. Micheal Vick. Both are good quaterbacks, but obviously two very different styles of play.