To understand where physical strength comes from, you need to become familiar with the theory of muscle building. As you know, human muscles consist of three types of muscle fibers
Type I – slow-twitch aerobic
Type II A – fast-twitch oxygen
Type II B – fast-twitch glycolytic
Type I gives low strength and speed, but high strength. Type IIB – high strength and speed, but low durability. Type IIA, on the other hand, fibers with intermediate properties. The benefits of having the right fiber composition in your muscles are obvious. Long-distance runners usually have leg muscles consisting of 75% of type I fibers, while sprinters and strongmen are equipped by nature with muscles consisting of 75% of type II fibers.
Why do muscle fibers have such very different characteristics? Science is constantly making progress in exploring this issue, which until recently has not been clarified. It is a bit like exploring the structure of the atom and searching for more and smaller elementary particles. In the case of muscle fibers, it was found that their characteristics are mainly determined by the content and composition of MHC’s heavy chains, but that’s not all. These chains contain isoforms that also exist in three types I, Ha and IIx, corresponding to type I, IIA and IIB fibers . Regarding the light MLC chains, it was only found that they generate only some of the above properties, are present in the minority and are not yet fully investigated.
Why do we have to go so far into anatomy to understand the basics of strength development? It is enough to realize that MHC IIx chains shrink at a rate 5 to 10 times higher than MHC I chains, and also greater than MHC II chains. It becomes clear that people with MHC II type fibers, especially MHC IIx, in their muscles are predisposed to power-speed disciplines. It used to be said that they have “innate strength,” and now we know what it is. Therefore, genetic predisposition determines the predispositions of strength, but it has also been found that various forms of mechanical and electrical stimulation of muscle fibers favorably improve their strength capabilities. And this is the scope of increasing strength, which we can influence through skillfully conducted trainings.
Now let’s look at how different types of workouts and periods of training affect muscle changes.
Recently, a number of precise studies have been carried out in scientific institutions answering this question. In one of the tests people performed typical bodybuilding training for 3 months, and later, for the next 3 months, they did not train. The results may be surprising to us, but scientists have long expected that. After the training period, the number of MHC IIx fibers decreased from 10% to 4%, while the number of MHC I fibers increased from 49% to 51%. So there were changes that we do not really want.
What happened then? When the tests were repeated after the training period, it turned out that the number of MHC IIx increased from 4% to 19%, and MHC I decreased from 51% to 45%. Thus, the MHC IIx jump at 19% is a significant exceedance of the initial level (10%). This is what the representatives of strength and speed disciplines dream about.
Other studies have gone even further. People who regularly train with previously non-training were compared. When using the training – training – training course, it turned out that after the first training period (20 weeks) MHC IIB fibers decreased from 16% to 1%, after a period of training (32 weeks) increased from 1% to 24%, and after the next period Training (6 weeks) fell from 24% to only 13%. This best shows the correctness of using the cyclicality of training. After subsequent cycles, the number of type II fibers will consistently increase.
These results have been confirmed in many other studies, such as bodybuilding and related training have always led to disadvantageous changes in heavy myosin chains from the point of view of strength and speed, resulting in a decrease in MHC IIx fibers in favor of the growth of MHC II and MHC I fibers, and so this type of training is not recommended for athletes seeking to increase strength, speed and dynamics.
What may be more surprising, the reduction of MHC IIx in favor of MHC I was also observed in sprinters training in the preparatory period for the competition, but despite this they slowly improved their results, because it is affected not only by muscle fiber composition, but also elements such as size nerve impulses, mental-muscular coordination and other factors.
And what caused the reverse transformation, i.e. the increase in MHC IIx fibers and the decrease in MHC I? Here, we can also be surprised, but the increase in MHC II was found after periods of debauchery, immobility, decline in nervous system activity (spinal injuries) or after reduction of loads (eg while in the state of weightlessness during spaceflight).
Researchers do not know yet what mechanisms are behind such changes. There are many theories. The most probable is that it is the result of adapting the phenotype to the requirements imposed by environmental conditions, and thus the endeavor of the organism to survive. Paradoxically, the reduction of fast twitch fibers for slow twitch seems to be a weakening of the body in the face of large mechanical overloads. Can there be any benefits to it?
First of all, the body becomes more efficient in this way from the side of metabolic changes, which is important in the face of shortages it has to cope with. Secondly, it was found that under certain conditions (maximum stimulation both during the concentric and eccentric motion phase) the body switches to the use of MHC Ha fibers, which are able to generate even or even greater strength at much lower velocities of motion.
Therefore, two methods seem to be the most beneficial for use in strength training or an exercise with such weights that will stimulate the muscles during both concentric and eccentric movement and the use of moderate speeds, or mainly using the concentric phase of motion at very high speeds.
Researchers are also trying to explain why after the period of deprivation or reduced activity the body “allows for such a large increase in MHC IIx fibers. Reduced activity entails less energy and muscle endurance, so the previously acquired high metabolic efficiency is no longer needed. The body can then afford to work with reduced metabolic efficiency, which accompanies the use of fast twitch fibers, which, after all, have their own great advantages.
In strength sports, such as powerlifting, dynamic force is needed to start and fight quickly. There is a starting power and explosive strength. The starting force allows the immediate inclusion of as many muscle fibers as possible. It is necessary to strive to overcome the inertia of the bar as quickly as possible, before the ATP supplies are exhausted, which at the maximum voltage of almost all muscles occurs after about 2 seconds.
After incorporating muscle fibers into work, we must try to keep them in working condition at maximum effort for a specific period of time. This is called an explosive force. She is to provide the acceleration of the weight so needed to pass through the critical point and successfully complete the approach in each of the three buoys. The fight must be completed before the majority of muscle cells are exhausted. For all that, the most efficient work of fast twitch fibers is needed, including the appropriate release of ATP *.
Currently, most researchers agree that aerobic training or other types of endurance training reduce the ability of the neuromuscular system to generate maximum strength, which is associated with adaptive processes in the muscles. Fast twitch fibers are mechanically destructed mainly during the eccentric phase of repeated movements and are replaced by slow twitch fibers, and enzymatic and neuro-muscular changes occur in the direction of preference for slow-twitch fibers.
Therefore, the triathletters and athletes of other speed-strength disciplines are being discouraged from using aerobic (endurance) training in order to reduce body fat before take-off. It is unfavorable to perform aerobic training together with strength training (on the same day) or on other days (alternately). Adequate level of adipose tissue should be maintained through proper nutrition and should not increase by more than 2% in relation to the starting state in the non-regression period.
Strength training combined with endurance training may be useful only in strength disciplines in which occasional explosions or efforts occur from time to time.
Practical observation shows that many triathlonists perform only a slow repetition with constant muscle tension. Considering what is mentioned in this article, they should remember that fast twitch fibers generate explosive power and decide on maximum strength. Therefore, dynamic explosions should also be included in the training.