Q. What is the difference between slow twitch and fast twitch muscle fibers? Why is it important to work both?
A: Let’s talk about muscle. Muscle allows the body to turn energy into motion. You won’t be able to do anything without muscle tissue. You have more than 600 muscles in your body. They help you move, lift things, pump blood through the body, and even help you breathe. Pretty cool, huh? I’m sure you’ve also heard about slow twitch and fast twitch muscle fibers, or Type I and Type II…Getting a bit more specific here. Little confused? No problem. Keep on reading and you’ll find out more about each and what they do.
I like to keep it simple and try to explain science in simple English. Type I (slow twitch) muscle fibers dominate in an elite distance runner’s body. They are trained in endurance. Think about running for a long period of time, at a steady pace, medium intensity; these fibers are fatigue-resistant. They also produce less force than Type II fibers and that’s the main reason why they can last a lot longer. Marathon runners, bikers, or swimmers for example, work on running endurance, which occurs when the slow muscles use oxygen to create energy for long-lasting muscle contractions.
On the other hand, Type II, fast-twitch muscle fibers, are associated with strength and power. Think about super heavy squats or sprinting. How much you can do? How long can you last? Not long. Your fuel runs out quickly. These fibers fatigue super fast. Fast twitch fibers use anaerobic metabolism for fast energy instead of oxygen; the muscles get the energy faster, and in fuller force, but do not exhibit endurance. When we think of Type II fibers, we typically picture Olympic lifters, track sprinters, baseball players, and bodybuilders.
Everyone has a mix of both types of muscle fibers. People who have major disparity between muscle fibers often end up being elite athlete (genetics play a huge role). If you have a specific goal, you’ll gear your workouts towards Type I for endurance training or cardiovascular health or Type II for strength, agility, and bone density. Make sure not to neglect one or the other. Your workouts should include both the heavy loads necessary to stimulate what I call the “Big Boys,” the Type II fibers, as well as the lighter loads that do a better job getting the “Slow Boys” or the Type I fibers to grow.
One Healthy Breakdown: Now we know all about muscle fibers and that it is important to have some balance of the two types of exercise for overall fitness!
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