💪🏿💪🏻PT CORNER: Slow Movement for Strong Muscles 💪🏾💪

By: Reagan Rupard

Why do we move so slowly at Fierce45? You might have heard a coach mention using slow movement to build long and lean muscle, but what does that really mean?  To understand the benefits of slow control for building lean muscle, first, you’ll get a little anatomy lesson. There are two main muscle cell types in your body: type 1 fibers (slow twitch) and type 2 fibers (fast-twitch).

Slow-twitch muscle fibers are constructed to be more efficient over time. They contract more slowly and produce less power, but the cells are stocked with lots of mitochondria (you remember the powerhouse of the cell?!) that ensures 24-hour energy production for constant work. These cells are concentrated in our deep postural and stability muscles, those muscles that stay turned on all day to keep us upright. Think of an endurance runner when you picture slow-twitch fibers: they are lean, but can work for a really long time!

Fast-twitch muscle fibers are constructed to provide huge bursts of energy with fast, powerful muscle contractions. Rather than containing lots of mitochondria to produce constant energy, they store up an energy supply that gets burned up quickly. These muscle cells are more concentrated in our superficial muscles like our calves and the muscles of our arms. Think how quickly you run out of steam during an all-out sprint - that’s your fast-twitch muscle fibers running out of their stored energy! When you think of these muscles, imagine a sprinter.

These two muscle types work in different ways and therefore require different types of training to be strengthened. We train fast-twitch muscle cells with powerful movements against heavy resistance like jumping, sprinting, or lifting heavy weights with lots of self-generated momentum. When fast-twitch muscle fibers get stronger, they get bigger! This is why your friends who work out at Crossfit or in a similar style of exercise modality may tend to have greater muscle bulk - their fast-twitch fibers have grown to store more energy and have gotten larger to produce more powerful contractions.

Slow, controlled movements and strengthening against lighter resistance for longer periods of time improve the efficiency of our slow-twitch muscle fibers, causing the muscle cells to improve their energy production factory with more mitochondria. This means that these muscle cells are better and working hard for us all of our waking hours, and can provide more stability without fatigue during activities like skiing, running, and hiking. Beyond the aesthetic bonus of building leaner muscles as a result of increased energy demand without a large gain in muscle bulk, these muscles fulfill a protective role for our body, being there to stabilize and control movement in moments where you’re off balance or make unexpected contact with another object. Because they are most concentrated in our deep stabilizers around our joints, THIS is where you get the benefits of injury prevention and longevity in your sport outside of Fierce45. This is what, as a PT, gets me excited about having you on the machine moving slow and working hard. For more on how Fierce45 helps to prevent injuries, tune in to my next blog post.


Next time you’re in class and feeling that deep burn while the coach is telling you to keep moving more slowly, remember why. You truly are building more long and lean muscle fiber that is improving your body’s endurance and protecting you in the long run. That moment when you feel fatigued and your body wants to start using momentum to move the carriage, that’s the point where your body, if you choose to keep moving slowly with control, is making incredible strength gains.

Jessica Sharpe