Diversity of Muscle Fibers and Their Impact on Training

You can do a set of repetitions for your entire life and simply foster your development through weight progression, increasing the number of sets, or shortening breaks, but if you want to maximize the body's potential for hypertrophy, you should take into consideration the proportions of muscle fibers. It has been assumed among trainers that the 16 repetition range is going to be a muscle strength building scheme, and the 712 is used to stimulate muscle growth, but maximizing muscle mass or shortening your breakthroughs requires more power. But you should first understand the physical structure of your body for muscle tissue tissue, because it's important to know if you're going to increase muscle mass after you've done this kind of exercise, and if you can't do this type of exercise with just one muscle mass, then you'll be able to do it after you know the most commonly used type of muscle strength training, but you can do it at the same time. There are two types of muscle fibers – type I (slow-twitch) and type II (fast-twitch). Type II is divided into IIa and IIb. There are no muscles created solely from one type. However, in some muscles, a certain type predominates. And although it is worth using different repetition ranges to stimulate all muscle fibers, we should spend most of our time with training suitable for the dominant type of fibers. Although the fiber composition of each muscle is individual, the differences vary between 5 and 10%. Can the type of muscle fibers be changed? In fact, some studies have shown that high-intensity training can convert slow-twitch fibers into fast-twitch fibers. This is good news, because the percentage of fast-twitch muscles decreases with age, and this process begins after 30 years of age. Is there a test to find out which fiber type predominates in a particular muscle? One way is to find your 1 RM (weight with which you can perform only one repetition), subtract 20% from this weight, and perform the maximum number of repetitions. If someone does less than 8 repetitions, the muscle probably has an advantage of fast-twitch fibers, if more – slow-twitch fibers. A similar method is used by Charles Poliquin, one of the greatest authorities in the field of strength training, but he uses 85% 1 RM and the limit of 5 repetitions. However, this test also has drawbacks. First, you have to choose an exercise that really isolates the muscle. How do you test the quadriceps with the help of squats? Many muscles are involved in this exercise, starting from the gastrocnemius and ending with the gluteus. There is a high probability that you will receive incorrect data if the weakness of another muscle is determining the crossing of the 8-repetition threshold. Limiting factors are also technique or the nervous system. Unfortunately, it is not easy to check 1 RM at isolation exercises. You probably won't test the maximum strength on leg extension machines or chest press machines. Fortunately, there is enough research on the percentage distribution of fibers in muscles. Therefore, I will describe how to train these muscle groups most of the time, but I probably don't need to add that it is also worth using methods completely opposite, since we have already established that there are no muscles consisting only of one type of fibers.

Muscles with a long contraction duration should be trained with higher volume and frequency, and lower intensity and shorter breaks. The high fatigue resistance is due to the fact that muscle working time can be measured in hours. However, this comes at the cost of strength, as muscles made up mainly of fibers with a long contraction duration produce relatively low strength. As type I fibers promote long-term work, their training will be beneficial for those who train in disciplines such as marathon or cycling.

High-speed muscle fibers perform exceptionally well with less training volume and frequency, but with higher training intensity and longer recovery periods. Fibres IIa utilize oxygen processes more intensely, while fibres IIb use glycogen very quickly, utilizing oxygenless processes to meet their energy needs. High-speed fibers react better to muscle growth than slow-speed fibers, increasing their size by about 20%. Athletes such as runners, jumpers, basketball players, and others who participate in team sports should focus primarily on training high-speed fibers.

The chest muscles are made up of 60% high-speed fibers, which indicates that training should be conducted in low to medium repetition ranges and in medium to high weight ranges. The triceps muscles are made up of 67% fast-twitch fibers, which means that the best combination will be high intensity and repetition ranges from low to medium. The shoulder muscles are made up of 40% fast-twitch fibers, which means that training should be conducted in low to medium repetition ranges and in medium to high weight ranges. The biceps muscles are made up of 55% fast-twitch fibers, which means that training should be conducted in low to medium repetition ranges and in medium to high weight ranges. The forearm muscles are made up of mostly slow-twitch fibers, which means that training should be conducted in high to very high repetition ranges.