Types of Muscle Fibers

Hey Kids,


Today we are going to talk about boring anatomy. Why? because if you want to know how to grow your muscles, you must know what those muscles consist of.

There are three different types of muscle fibers within skeletal muscle. Understanding all three types will help you with exercise selection. For example, if the you’re a power lifter, you would want to focus on building maximum strength as opposed to exercise endurance. Knowing the different types of muscle fibers also helps to prevent injury because Type 1 (slow-twitch, red fiber) are resistant to injuries but have less ability to generate much force  (Hatfield, F. 2018 “Fitness: The Complete Guide”. Pg. 106). Type 2a  (fast-twitch, intermediate) fibers are larger and stronger but, more susceptible to injury and cramping and Type 2x are extremely strong but have no endurance and low recovery (Hatfield, F. Pg. 106).

Type 1 muscle fibers are slow twitch and create low intensity contractions that are best for endurance athletes (Hatfield, F. 2018 “Fitness: The Complete Guide”. Pg. 105). Activities such as long distance running, triathlons and even boxing mostly utilize type 1 muscle fibers. And, these types of athletes tend to possess more of these muscle fibers than other types of athletes such as bodybuilders and power lifters. This is because the slow twitch muscle fibers are made more for time than intensity and generate adenosine triphosphate (ATP) through the transfer system of aerobic energy (Hatfield, Pg. 105).

Usually an Ectomorph body type would perform the type 1, slow twitch muscle fiber activities such as aerobics, spin class and marathons because they are long and lean with difficulty building muscle (Snape, J. Sept. 1, 2017. “Ectomorph, Endomorph and Mesomorph: How To Train For Your Body Type”. coachmag.co.uk/lifestyle/4511/).

Although, a Mesomorph could also possibly perform these types of activities in that they are muscular with a high  metabolism and responsive muscle cells (Snape, J., 2017). In order to optimally perform these types of activities, one would train the body to become more efficient at maintaining oxygen for longer periods of time under various stressors such as elevated treadmill running, aerobic endurance classes that mirror the “Insanity” workouts because these last approximately an hour or more and are excellent in increasing endurance and stamina for different types of movements. Also, if you have the goal of improving type 1 muscle fiber count and abilities, you’d perform high repetition, low weight exercises as well to increase muscular endurance for those long bike rides or basketball games. The increase in muscular endurance would significantly benefit this long and lean individual without adding bulk or slowing you down in your sport.

Type 2a muscle fibers are fast twitch and can produce a lot of force for a considerable amount to time. These fibers are recruited for high intensity but shorter durations of activity such as bodybuilding, crossfit and sprinting. The problem is that they tire out faster and can cramp up easily as they are more vulnerable to lactic acid buildup. The Mesomorph would more likely possess more of the Type 2a muscle fibers because she is muscular and naturally well built and easy gainers of muscle with very responsive muscle cells (Snape, J. 2017). The Endomorph could possibly contain these fibers but less of them because he is larger with higher body fat. Often this person has a more round body shape and stores more body fat than they build (Snape, J. 2017). To train this person to better perform their activities, I would definitely have them lift more weights and increase the workload slowly over time to increase muscle hypertrophy. The goal for this person is to lift weight or pull up better or to perform more bodyweight exercises. For example, the crossfitter would ideally want to increase their amount of fast twitch fibers for those box jumps or cleans. Lots of plyometrics would help this person reach their goals.

Finally, Type 2x are fast twitch muscle fibers like type 2a but, they are even more strong yet they fatigue and become injured much easier (Hatfield, F., 2018, Pg. 106).  These type 2a fibers belong to the sedentary Endomorph who has more body fat due to lack of exercise. They are possibly given to this person for emergencies such as having to run away from something but, once they are used for exercise, they do not rebuild and are usually lost (Hatfield, F. 2018, Pg. 106). This person would surely lose these fibers in whatever program they are given but, the good thing is that they can acquire “new” muscle fibers. Depending on whether their goal is to build endurance, strength or both; a trainer can assist them in acquiring all new, stronger muscle fibers. The best approach is an all around training program that contains cardio and strength training. The best method in my opinion is circuit training. We could mix up cardio, bodyweight and resistance exercises while also incorporating balance and core stability/strengthening exercises to build their new body from the inside out!


Email me for any tips or if you have questions……

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