Muscle fibres and their influence on the training process
Each of us wants to look good. Those who mean it, do something for it – they do some sports, eat well, take care of good sleep and sufficient regeneration. But how many of us know our bodily parameters perfectly? We bet that most of us know our body weight, height, waist circumference, the more pedantic ones know circumference of arms, thighs and the like as well. However, a perfect knowledge of your body parameters can substantially contribute to even better results in the training process and help us achieve the desired goal. One of such especially important parameters is the ratio of fast and slow muscle fibres, which we will talk about more in this article.
PHYSIOLOGICAL BASIS
We know three basic types of muscle - smooth, transversely striated (skeletal) and cardiac. Smooth muscle is not controllable by will and can be found, for example, in most internal organs. The cardiac muscle is specific in that, although its microscopic structure corresponds in quality to the structure of skeletal muscle, its properties are close to smooth muscle - the activity of the heart, as in the case of smooth muscle, is not controllable by the will. The last type, skeletal muscles, will be of most interest to us for the purposes of this article. They have a transversely striped structure, they are controllable by the will and their individual cells, i.e. the fibres are grouped into so-called motor (moving) units. One such unit is a group of fibres innervated by one particular nerve cell [1].
skeletal muscle
It makes up about half the body weight of the human body. Each muscle consists of so-called slow (red, type I) and fast (white, type II) fibres. Their relative proportions depend on the rate of contraction required of the muscle in question.
Slow fibres
They are thin, richly congested and contain a large number of mitochondria (part of the cells responsible for their energy management). We find in them a large amount of myoglobin protein, which, like haemoglobin in the blood, is responsible for the transfer of oxygen to cells, in this case muscle cells. Slow fibres are used for longer-term muscle work of lower to medium intensity, which is characteristic for endurance sports (such as marathons).
Fast fibres
They are thicker, less congested and contain less mitochondria. From this point of view, it can be considered that they do not need as much oxygen as slow fibres and function primarily on anaerobic metabolism. Fast muscle fibres are used in short-term muscle work of medium to high intensity, which is typical for explosive sports activities (e.g. tennis, sprints).
THE RELATIONSHIP BETWEEN FAST AND SLOW FIBRES AND THEIR INFLUENCE ON SPORT PERFORMANCE
According to current knowledge, the ratio between fast and slow muscle fibres is genetically determined. This also involves the potential of the athlete for that discipline. It is more than likely that Usain Bolt would never be an Olympic marathon winner, as well as breaking Bolt's world records in the 100 and 200 meters would not be manageable by any of the best marathons.
You can still find claims in many sources today that the ratio of fast and slow muscle fibres is about the same, but it is a myth. The fact is that this ratio differs not only between individual muscles, but also between different persons for the same muscle.
For example, the quadriceps femoris has, in average people, a 55:45 ratio of fast to slow muscle fibres in favour of fast fibres. In contrast, for sprinters this ratio is 63:37 and for marathon runners 18:82 [2]. The metabolism and cross-section of muscle fibres in a given muscle can be influenced by suitably selected training to such an extent that it is directly proportional to the proportion of fast muscle fibres.
DETERMINATION OF THE RATIO OF FAST AND SLOW MUSCLE FIBRES
For our needs, we will omit the description of methods typical especially for the field of scientific research and sports medicine. You can also find out a rough idea of which fibres predominate in our body in the gym. To explain, we will use pressure with a large barbell on a straight bench as an exercise, but you can, of course, use another exercise that will suit you better. At the beginning, it is particularly important to know what your repetition maximum (1RM) is. Let's say your maximum for this exercise is 100 kilograms.
The test should be performed as follows:
- 6 repetitions with an empty rod
- 5 replicates with 60 percent 1RM
- 3 replicates with 75 percent 1RM
- 2 replicates with 85 percent 1RM
- 1 repetition with 90% 1RM
- 3-minute break
- 1 repetition with 1RM
- 5-minute break
Then perform as many repetitions as you can with 75 percent 1RM. Do all the repetitions at the same pace, moving down for 4 seconds and then moving upwards explosively. If you can do 4-6 repetitions, your pectoral muscles are made up mostly of fast fibres. If you can do more than 12 repetitions, your pectoral muscles are made up mostly of slow fibres [3].
how to use information about the mutual ratio of muscle fibres
It is important to note that this article will probably be most beneficial for some advanced exercisers. In the case of beginners who do not have sufficient experience with bodybuilding (or with any regular sport), they achieve rapid gains in both mass and strength due to the nerve activation of a larger number of muscle fibres [4]. Knowledge of which type of muscle fibres prevails in the relevant part of the body is most used by regular trainers for at least a year. But simple principles apply to everyone - a rationally balanced diet, nutritional supplements in the form of quality proteins, creatine or amino acids, sufficient caloric intake, training with a progressive increase in load, quality regeneration and good sleep.
As for the exercise itself, for individuals with a predominance of fast muscle fibres, the optimal number of repetitions to stimulate their growth is at the level of 1 to 12 repetitions. In individuals with a predominance of slow muscle fibres, 12 is minimum, the maximum is the number of repetitions that will cause the muscle to fail. Otherwise, both groups can (and should) follow the basic principles: 3 workouts per week, 1-2 exercises exercising a certain muscle group, 2-3 series of one exercise, weight of the load at a level of about 60 percent of the maximum.
SOURCES
JAVORKA, K. et al. Medical physiology. 4th revised and supplemented edition. Bratislava: Osveta, 2014. ISBN 978-80-8063-407-0. 770 p.
GANONG, W.F. Review of Medical Physiology. London: Prentice-Hall International, 1995. 781 p.
EHRMAN, J.K. et al. Clinical exercise physiology. Human Kinetics Publishers, Inc., 2003. 619 p.
TURECKÝ, L. Medical biochemistry II. 2nd revised and supplemented edition. Bratislava: Asklepios, 2002. ISBN 80-716-7050-2. 189 p.
