Striated muscles are composed of two types of fibers: slow twitch and fast twitch. Slow twitch fibers are used in activities that must be sustained over a long time, such as distance running. They have a high capacity for aerobic energy production and can remain active for a long time while producing relatively small amounts of lactic acid. This is important because lactic acid build-up in the muscle tissue causes the muscle to fatigue and eventually stop working. The ability to maintain low levels of lactic acid means an increased capacity for work. People who have a high percentage of slow twitch fibers excel at endurance activities.
Fast twitch fibers are used in activities that require explosive power for a short duration, such as sprinting or sparring. They have a great capacity for anaerobic energy production, which allows them to produce intense power and speed of contraction; however, this also causes them to accumulate large amounts of lactic acid and fatigue quickly. People who have a high percentage of fast twitch fibers excel at activities that require explosive power.
Therefore, to develop sparring abilities, it would seem best to increase the percentage of fast twitch muscle fibers in your body. Unfortunately, this is not possible. The ratio of fast and slow twitch muscle fibers is determined early in life and cannot be markedly changed. Studies have shown that distance runners have high percentages of slow twitch fibers and sprinters have high percentages of fast twitch fibers but that the activity in which they participate is not responsible for these percentages. Instead, it is believed that some people participate in endurance sports because they naturally excel in this area. In the same respect, people who are naturally fast tend to participate in sports that require speed and power.