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Muscle Fiber Types

QUESTION:

My sister is an accomplished long distance runner and says that I should take up running too because I'm probably genetically suited for it. I've heard that genetically, a person's muscle fibers are either made for aerobic type activities like running, or anaerobic activities like jumping or sprinting. Is this true?

ANSWER:

Yes, athletic performance is closely tied to many genetics factors including muscle fiber type. There are different types of muscle fibers and nerves that stimulate muscle contraction. These nerves and muscles can be grouped into two main categories: slow twitch (aerobic) and fast twitch (anaerobic). Slow twitch or aerobic muscle fibers have a high capacity for the use of oxygen for energy. The more slow twitch fibers an athlete has, the more he or she is suited to long duration exercise, such as middle to long distance running, and the less he or she is suited for explosive activities. The opposite is true for a person with more fast twitch or anaerobic muscle fibers. However, everyone has a mix of muscle fibers and thus everyone has some capacity to perform a wide variety of activities from aerobic to anaerobic. Thank goodness for this beautiful design or else we'd all be incapacitated in one form or another!

When we choose activities to participate in, we tend to migrate toward events or sports that we do well at. Usually this selection, by success or failure, matches us to our most genetically suited activities. However, athletes who are triumphant will not only be genetically gifted, but will also have the motivation, desire and love for their sport that is necessary for success. Nevertheless, genetics can explain why some of us, no matter how hard we try, just cannot attain a predetermined athletic goal. The message here is to recognize your strengths and weaknesses, and to make your goals realistic for YOU.

Unfortunately, just because a relative is gifted in a certain sport does not necessarily mean that you will be also. Depending on your "luck" in the genetic draw of life, you may be very different from a sibling. I think the best attitude to take is that each and every person's genetic makeup is a gift. If running is something that you have a desire to pursue, then by all means give it a try. If not, then I'd suggest finding something that is more tempting to you, as interest and motivation are as important as your genetic design when it comes to choosing activities.

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Our expert, Dr. Sharon E. Griffin, holds a B.S., M.S., and Ph.D. in the areas of exercise science/physiology. She also holds a second M.S. degree in Nutrition and is a licensed nutritionist and an ACSM certified health and fitness instructor.