- There are two types of muscle fibers (cells found in muscles tissues) in all of our muscles. They are called Fast Twitch and Slow Twitch and they both have two distinct functions. The Fast Twitch Fibers can provide an extreme amount of power for a short period time—anywhere from a few seconds to a minute. The Slow Twitch Fibers, however are key in endurance. They provided a prolonged strength of contraction over several minutes and into hours.
- The differences stem from how they process energy to be used for work. Fast Twitch fibers have a high amount of stored glycogen, but also produce a large amount of lactic acid, which induces quick fatigue. Slow Twitch Fibers convert fats and sugars to generate energy for movement and do not produce lactic acid making them resistance to lactic acid mediated fatigue.
- Our bodies have different ratios of Fast Twitch to Slow Twitch Fibers depending on the muscle groups. Postural muscles (back muscles) for instance have mostly slow twitched fibers, which make them less prone to fatigue. Muscles used in more dynamic movements like heaving lifting or jumping (biceps and quads) have mostly Fast Twitch Fibers.
- Fast Twitch to Slow Twitch Fibers differ not only among muscle groups, but also individuals. Some people are born with more of one than the other. In fact, the ratio of fibers may be genetically controlled since athletic conditioning will not change this ratio. So if Mo had a more ideal ratio of slow to fast twitch muscle fibers than the average Joe (pun intended) would that set him up for success?
- Predominant muscle fiber types is just one piece of the puzzle. As you may have guessed many other factors contribute to athletic achievement whether the runner is novice or seasoned. Research has shown that physiological, biochemical, neurological and biomechanical systems all contribute to the success of an athlete. In other words, even if Mo Farah was born with the ideal muscles for long distance running, it is most likely that his physical training, mental skills, and overall genetic composition led him to Olympic Gold.
What are your thoughts? Do you think elite athletes are born or made?
McArdle, W. D., Katch, F. I., & Katch, V. L. (2006). Essentials of exercise physiology. Baltimore, MD: Lippincott Williams & Wilkins.