By Matt Brown
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March 12, 2023
Never increase the quantity of stimulus at the expense of quality. 👊 It’s pointless to perform sets where the resistance is reduced so much so…that you don’t train the appropriate motor units and don’t create sufficient tension on the muscle to elicit gains. If your goal is to increase muscle mass…you’re best to train the different fibers that make up a muscle. 🔥 Muscle fibers can be classified into different types based on their contraction speed, force generation capacity, and their ability to use different energy sources. The three main types of muscle fibers are: ✅ Slow-Twitch Fibers…Type I ✅ Fast Twitch Fibers…Type IIa and Type IIb ✅ Intermediate Fibers Slow-twitch (Type I) fibers: These fibers contract slowly and generate less force, but are highly resistant to fatigue, making them ideal for endurance activities. Slow-twitch fibers primarily use aerobic metabolism to generate energy and are rich in mitochondria and myoglobin. Examples of muscles that contain mostly slow-twitch fibers include the Soleus, the muscles of the back, and the postural muscles. Since these fibers are highly resistant to fatigue, they are best trained using higher rep ranges (15-20 reps per set or more) with lower weight. This type of training can improve muscular endurance and promote the development of slow-twitch fibers when taken to failure. Fast-twitch (Type II) fibers: These fibers contract rapidly and generate high amounts of force, but fatigue quickly. Fast-twitch fibers can be further classified into two subtypes: Type IIa and Type IIb. Type IIa fibers have a higher resistance to fatigue than Type IIb fibers and can use both aerobic and anaerobic metabolism to generate energy. They are well-suited for activities such as sprinting and middle-distance running. Type IIb fibers, on the other hand, are primarily anaerobic and are used for short, intense activities such as weightlifting and jumping. Examples of muscles that contain mostly fast-twitch fibers include the Biceps, the Quadriceps, and the muscles of the upper body. Fast-twitch (Type II) fibers: These fibers are best trained using lower rep ranges (i.e., 1-6 reps per set) with higher weight. This type of training can improve maximal strength and promote the development of fast-twitch fibers. Intermediate fibers: These fibers have characteristics that are intermediate between slow-twitch and fast-twitch fibers. They can use both aerobic and anaerobic metabolism and can generate moderate amounts of force for moderate periods of time. Examples of muscles that contain intermediate fibers include the Gastrocnemius and the Hamstrings. Since intermediate fibers can adapt to different types of training, they can be trained using a variety of rep ranges and weights. However, moderate rep ranges (i.e., 8-12 reps per set) with moderate weight may be optimal for promoting hypertrophy (muscle growth) in intermediate fibers. It's important to note that while muscles may contain different proportions of each type of fiber, they are not strictly limited to one type. Rather, muscles can adapt to different types of training and activities, resulting in changes in fiber type composition. Matt Brown Coach