One of the two major muscle fiber types in the human body, slow-twitch muscle fibers, also known as Type I muscle fibers, are responsible for activities that demand endurance like marathon running, long-distance swimming, cycling, hiking, and even dancing.
These muscle fibers are characterized by their extraordinary oxygen uptake capacity, enabling them to contract for an extended period of time without becoming fatigued. Due to their high quantity of myoglobin, a protein that stores oxygen, they are known for their red color.
Compared to fast-twitch muscle fibers, slow-twitch muscle fibers are smaller and produce less force, but they are more resistant to fatigue, making them crucial for endurance activities.
They have a higher aerobic capacity because they have more mitochondria, the cell's energy-producing organelles, than are found in fast-twitch muscle fibers. Slow-twitch muscle fibers are better supplied with nutrients and oxygen due to their higher capillary density.
Slow-twitch muscle fibers can grow in size and strength through consistent training. However, this size increase is not as significant compared to fast-twitch muscle fibers, which are responsible for explosive movements like jumping and sprinting. Endurance training, such as long-distance running or cycling, can boost slow-twitch muscle fibers' oxidative capacity and fatigue resistance.
Incorporating strength training with high reps and low weights will also help you improve your endurance by concentrating on your slow-twitch muscle fibers.
The Alpha Progression app is great for measuring your progress and creating a customized training plan. With the app's plan generator, you can, for example, strengthen your slow-twitch muscle fibers and create a plan to improve your strength endurance.