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Have you ever heard a coach say the term “fast with” or “slow twitch” muscles fibers during class? Then immediately thought, huh? Well, you are not alone.

Your body has two basic types of muscle fibers: slow twitch (Type 1) and fast twitch (Type 2). As the name implies, slow twitch muscle fibers are designed to do sustained work for an extended period of time - think long distance runner. Fast twitch fibers are for quick, explosive movements designed for short term movements - think of a sprinter. Each muscle in your body has both types, but in different proportions based on the primary function of that muscle. For example, the muscles of the neck and back that help to sustain your posture and keep you upright all day without getting tired are primarily slow twitch fibers.

Muscles like your gastrocnemius (probably the muscle you picture when you think of defined calves) and your biceps are fast twitch. When fast twitch muscles get stronger, they get bigger! Think of our sprinter again. To perform quick, explosive work, fast twitch muscle fibers build more contractile proteins to provide a stronger and faster contraction. These muscles are mostly superficial, and focusing on fast twitch work is excellent if you’re trying to get big and buff.

Slow twitch muscle fibers may get a little bit bigger, but they primarily strengthen by getting more efficient. Our body grows more blood supply to them, and they build more mitochondria (I know y’all remember the powerhouse of the cell from high school biology!) so that they have more of the supplies they need to do sustained work. These muscles tend to be our deeper postural muscles that surround our joints and provide all-day protection and stability.

FierceMovement is designed to target slow twitch muscle fibers with slow, slow work focused on retaining tension against resistance in the muscle but never using momentum. That way, we force slow twitch muscles to fight for 45 minutes without ever turning the work over to our fast twitch muscles.

Why is this such a big deal to use at Fierce45? GREAT QUESTION! The fact that these muscles get stronger and more resilient but not (a lot) bigger is how we’re able to build long, lean muscles that make a visible change in our body’s exterior. However, that’s hardly the most crucial part - strengthening slow twitch muscle fibers provides stability and delays fatigue in our body in a way that is truly functional in the real world. Fierce45 clients step off the machine and go out into the world as stronger and less injury prone skiers, runners, parents, professional football players, climbers, and dancers.

-Reagan Ruppard (Fierce Coach)