If you watch sports on TV, at some point you’ve probably heard a commentator talk about an athlete having explosive or powerful muscles. For example, professional football player JJ Watt has received a lot of attention for his off-season conditioning program, which includes flipping a large truck tire. A sportscaster was recently discussing Watt’s training techniques and mentioned that Watt was working on his fast-twitch muscle fibers in an effort to become more explosive. At first, this sounds kind of hokey—fast-twitch muscle fibers? Is that really a thing, and is it possible to do certain exercises that focus on one muscle fiber type? Show
The answers, in short, are yes and yes. Yes, there are different types of muscle fibers in the body, which are classified based on how they produce energy. Yes, the different muscle fibers can be trained using specific exercises designed to focus on how they create energy or generate force. While a variety of types of muscle fiber has been identified, including type I, type IC, type IIC, type IIAC, type IIA, and type IIX, they are generally classified as being either slow-twitch or fast-twitch (see table). 6 Things to Know About Slow-twitch, or Type I, Muscle Fibers:
As you can see, slow-twitch fibers have specific characteristics for how they function, which means they can be trained to be more aerobically efficient with the proper exercise program. Techniques for Training Slow-twitch Fibers:
8 Things to Know about Fast-twitch, or Type II, Muscle Fibers:
As you can see, the characteristics of fast-twitch fibers are more suited for explosive, strength- and power-based sports like football. Therefore, when an announcer talks about how a training program benefits a specific type of muscle fiber, they are being accurate with the science. If you want to engage more fast-twitch fibers to help you increase strength levels or become more explosive, here are a few specific techniques that work. Techniques for Engaging Fast-twitch Fibers:
Understanding how the physiology of the body adapts to exercise can help you develop more effective exercise programs for your specific needs. Genetics determines how much of each muscle-fiber type you possess; however, identifying whether you are fast- or slow-twitch dominant would require an invasive muscle biopsy. Therefore, if you find that you tend to enjoy more endurance-based activities and that they are relatively easy for you, you probably have a greater number of slow-twitch fibers. Conversely, if you really dislike going for long runs, but enjoy playing sports that rely on short bursts of explosive movements, or if you like weight training because it is relatively easy, you are probably fast-twitch fiber dominant. An exercise program that applies the right training strategies for your muscle fibers can help you to maximize the efficiency and enjoyment of your workout time.
What type of muscle fibers do marathon runners have?The two types of skeletal muscle fibers are slow-twitch (type I) and fast-twitch (type II). Slow-twitch muscle fibers support long distance endurance activities like marathon running, while fast-twitch muscle fibers support quick, powerful movements such as sprinting or weightlifting.
What is the predominant muscle fiber type being used in running?Type I, or slow-twitch fibers, are seen in high abundance in elite endurance athletes, such as long-distance runners and cyclists. Alternatively, fast-twitch IIa and IIx fibers are abundant in elite power athletes, such as weightlifters and sprinters.
Do marathon runners have more type 1 muscle fibers?The runners who had performance increases tended to have a higher proportion of type I fibers (also called slow-twitch fibers), which are the kind used most for endurance, rather than fast-twitch fibers that switch on with short energy bursts.
What are type 2B muscle fibers?Type 2B (FG) fibers primarily use anaerobic glycolysis as their ATP source. They have a large diameter and possess high amounts of glycogen, which is used in glycolysis to generate ATP quickly to produce high levels of tension.
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