The What's and How's of Gaining Muscle
April 15, 2021

A close second to weight loss when it comes to fitness goals is to gain muscle. Whether it’s to boost athletic performance, improve one’s aesthetic, or a combination of both, it’s important to understand how parts of the muscle, specifically muscle fibers, impact the goals one wants to achieve.

Coach Tinoy doing an upper-body workout


Skeletal muscles are made up of muscle fibers called slow-twitch (type I) and fast-twitch (type II). While this may all sound intimidating, it’s essential to understand the difference between these two types of muscle, and the training styles involved for both that will help you achieve your fitness goals.

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Slow-Twitch (Type I) Muscle Fibers

This type of muscle fiber takes longer to fatigue, which makes it great for long distance and endurance-based activities, and other prolonged exercises. They produce less force and are slower than type II or fast-twitch fibers when it comes to producing maximum muscle tension. Despite this being the case, they are able to maintain longer contractions, which are needed for stability and posture control. Slow-twitch muscle fibers are what work when one does marathons, power walking, and endurance training, or goes cycling and swimming. Steady and prolonged movements done in yoga and pilates work this type of muscle fibers too.


Fast-Twitch (Type II) Muscle Fibers

Fast-twitch muscle fibers, on the other hand, fatigue quicker, making this type great for sudden, fast-paced, and explosive movements. They tire faster than type I or slow-twitch muscle fibers, but yield greater force, which is beneficial for power activities and gaining muscle mass. Such exercises and activities that put this type of fibers to work include sprinting, powerlifting, strength and agility training, and even jumping


How to Train Accordingly

Before deciding to focus on specific activities that strengthen a certain type of muscle fiber, note that each person’s bodies and muscles are made up of both kinds of fibers, and that the ratio of both types is dependent on one’s age and activity level. 


We may have a 75%-25% split of kinds of fibers, depending on what kinds of exercises we’re used to, most especially if we favor certain types of movement over others. As for non-athletic people, a 50%-50% split may be more evident with them. With regard to age, we lose lean muscle mass as we grow older, fast-twitch fibers tend to decline as we age too. But, aging can also lead to an increase in slow-twitch fibers. Because this is the case, resistance training is highly encouraged, so that we lessen the risk of metabolic dysfunctions, changes in body composition, and falls.


While slow-twitch muscle fibers can be strengthened through endurance and low intensity training, its fast-twitch counterpart grows with strength training. For those looking to increase both types in one go, resistance training is your answer. Needless to say, endurance training done with high intensity can improve both fast-twitch and slow-twitch fibers, too.


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