If your goal is to PR in a marathon, climb a mountain, or crush your co-workers in the annual office plank competition, you need to understand type 1 muscle fibers and how to build them.
Of the two main types of skeletal muscle fibers, type 1 muscle fibers (“slow-twitch” muscle fibers) are more endurance-oriented and play an important role in stability exercises, high-repetition strength training sets, and isometric holds.
But before we get into the details of how to target type 1 fibers during exercise, let’s first take a closer look at what they are and how they work.
What are type 1 muscle fibers?
Compared to type 2 (fast-twitch) muscle fibers, type 1 muscle fibers, which are larger and stronger, have a longer contraction time (hence the name “slow-twitch”). As a result, they produce less force but are more resistant to fatigue.
That’s why they’re your body’s main wiring for long-term sustained activities like running and cycling, and sustained effort and high-repetition exercise like circuit training.
How to train type 1 muscle fibers
Every muscle contains type 1 and type 2 muscle fibers, and each person has a unique ratio, says Brenne Seliberti, a former assistant professor in the Department of Human Performance at the University of Tampa. But with targeted training, you can build and favor one type of phone over another.
Focus on aerobic and endurance activities and training methods to develop your type 1 muscle fibers.
1. Consistent training
A steady pace over long distances will hit your type 1 fibers (unlike sprints and interval training, which target type 2 fibers).
2. Resistance training
Incorporate light weight, high rep sets into your routine to target type 1 fibers. Studies show that performing both light/high rep and heavy/low rep sets can help increase hypertrophy (muscle building) by working both major muscle fibers.
3. Round training
Back-to-back plyometric, bodyweight, and weightlifting exercises will tax your cardiovascular system and your muscles, especially your type 1 fibers.
What do type 1 muscle fibers look like?
Type 1 muscle fibers are red because they require more oxygen to produce energy than type 2 muscle fibers. Their anaerobic (oxygen-independent) type 2 muscle fibers are white in color.
“Type 1 fibers are smaller,” says Seliberti. “On closer inspection, type 1 muscle fibers have a higher capillary density and oxidative capacity, and a smaller diameter than type 2 fibers.”
