Running Longer and Faster The Philippine Star >> News >> Sports: "Running involves a combination of aerobic (oxygen-powered) and anaerobic (absence of oxygen) activities.
Our running muscles have two types of fibers, the “Slow-Twitch” and the “Fast-Twitch”, which are randomly mixed depending on our genes. Fast-Twitch muscles are generally more powerful (and bulky) but they fatigue more easily, whereas the Slow-Twitch muscles are relatively weaker but are virtually tireless and efficient in consuming oxygen (aerobic).
Marathoners (42 Kms) and ultra-marathoners (more than 42 Kms) have dominant slow-twitch muscles, which explain their awesome endurance to run long distances.
Meanwhile, sprinters running 100 meters up to 400 meters have a lot of powerful fast-twitch muscles fibers. Elite runners from 800 meters up to the marathon (42 k) have different combinations of these fibers. The longer the distance a runner excels, generally the more dominant the slow-twitch muscle fibers are."...