Performance activities lasting 10 seconds or less require tremendous amounts of energy to be produced in a short period of time and Type II muscle fibers understand be recruited. Individuals with a greater percentage of Type II fibers generally have an advantage over individuals with a high percentage of Type I fibers. Sports psychologists often refer to what is called the inverted U hypothesis of sports performance. This model helps explain why some good practice players are unable to perform optimally in game situations. Their arousal or anxiety levels are too high for performance to be optimal.
Training can have an enormously positive effect upon some individuals.
However, you cannot take the winner of the Boston Marathon and expect to turn him or her into a champion in the 100-meter dash or a champion power lifter, or expect training to turn Michael Johnson into a world class marathoner. Yes, within his genetic limitations. Training does not cause large-scale shifts in muscle fiber types. There are shifts within Type II subtypes. Training can improve the oxidative processes of some Type II fibers, enabling them to be more fatigue resistant and improve aerobic energy allocation.