All athletes know that the basic principle of strength training is to perform a given number of repetitions in an exercise to failure. That is, until the moment when the subsequent repetition becomes impossible.
But with all the apparent similarities of the failure repetition in any power exercise, the causes of failure at the second, sixth or fifteenth repetition are different. Let’s figure out what causes muscle failure at each particular repetition. Consider everything using the bench press as an example.
First Repeat Failure
This is not even a refusal per se, but the reason why the athlete does not raise the maximum weight in the first attempt, and in the second, having rested and tuned, he managed to overcome it. This reason is a nerve factor associated with the ability to recruit motor units. There is also a technical moment when the athlete is mistaken and makes efforts on the wrong trajectory of the projectile; but today we are talking about the physiological and bioenergetic features of failure.
Recruiting all your motor units is a very difficult thing, and you need to learn this specifically. Our nervous system must send so many impulses to the spinal cord so that 100% of all motor units are excited and all the muscle fibers involved in movement are activated. As a rule, athletes of a competitive level succeed by 90%, and for beginners and non-trainees, by less than 70%, so there is always a reserve.
The training of Bulgarian weightlifters according to the system of Ivan Abadzhiev was aimed precisely at ensuring that the athlete was able to activate all Anabolic Steroids for Sale. We will say “everything”, assuming 90%. 10% is an untouchable reserve in case of extreme life situations.
Remember the story of an old woman who pulled out a chest with belongings from a burning house, which was then hardly pulled by four men; or about the polar pilot jumping on the wing of an airplane when, turning around, he saw a polar bear in front of him? This is just from that opera. Under the influence of extreme emotional stress, it is possible to recruit 100% of the motor units.
Failure in the second or third repetition
In the second repetition, the cause of failure can also be a nerve factor, that is, insufficient involvement of muscle fibers in the work, but there may already be another reason. When performing an exercise with a large weight in half a second of work, approximately half of the ATP supply located in the muscle is spent, which is restored in three to four seconds. If the second repetition is performed after one to three seconds, then the supply of ATP in the muscle is not enough to perform the next repetition.
I recall the physiology of muscle contraction
The contractile apparatus of muscle fiber (muscle cell) are special organelles – myofibrils. The number of myofibrils in the fiber reaches two thousand. Myofibrils consist of series-connected sarcomeres, each of which includes actin and myosin filaments. Bridges between actin and myosin can form in the presence of calcium, which enters the cell when it is nervous.
With the expenditure of energy enclosed in ATP, the rotation of the bridges can occur, i.e., the contraction of myofibrils, the contraction of muscle fiber and the contraction of the muscle as a whole. The energy of one ATP molecule is enough for one turn (stroke) of myosin bridges. The bridges disengage with the actin filament, return to their original position, adhere to a new site of actin and make a stroke. ATP energy is mainly required for separation. For the next stroke, you need a new ATP molecule. With an insufficient number of ATP molecules, the myofibril will not be able to contract, despite the presence of nervous excitation of the cell.
The amount of ATP in myofibrils is enough for one to two seconds of high-intensity work, but from the very first second of work in the muscle, the process of resynthesis of myofibrillar ATP takes place due to CrF (creatine phosphate). At the same time, the processes of aerobic and anaerobic glycolysis begin in the muscle. These processes are less powerful than the splitting of KrF, therefore, ATP molecules formed during glycolysis primarily go to the resynthesis of KrF, and only after the complete exhaustion of the reserves of KrF in the muscle go directly to ensure muscle contraction.
Aerobic glycolysis occurs in the mitochondria of OMV (oxidative muscle fibers) and PMV (intermediate muscle fibers). In them, the glucose molecule is split with the participation of oxygen, forming 38 ATP molecules, carbon dioxide and water. Anaerobic glycolysis takes place in the sarcoplasm of GMV (glycolytic muscle fibers), without the participation of oxygen. As a result of it, two ATP molecules and lactic acid are formed.
Lactic acid is a neutral molecule, but it can break down into lactate and a hydrogen ion. Lactate is a large molecule, therefore it cannot participate in chemical reactions without the participation of enzymes, for this reason it cannot damage the cell. The hydrogen ion is the smallest atom, besides it is charged, therefore it is able to penetrate into complex structures, where it leads to significant chemical damage.
Also, hydrogen ions prevent calcium ions from joining actin, which makes muscle contraction impossible. The more hydrogen ions, the greater the acidification of the muscle and the destruction of protein structures in it, the more difficult it is to perform the following repetition.
Failure in the fourth to sixth repetition
When working longer, the weight of the rod is correspondingly lower. The mechanism of recruitment of muscle fibers is included. Creatine phosphate is already beginning to be spent on restoring ATP, and the accumulation of lactic acid is already beginning. The reason for the failure is combined – due to the lack of ATP associated with the depletion of creatine phosphate reserves and the appearance of hydrogen ions, which make muscle contraction difficult.
Failure at the seventh to ninth repetition
The weight of the rod is even lower, respectively, the role of ATP deficiency due to muscle failure is reduced, since the process of ATP resynthesis with creatine phosphate is more active, and the role of hydrogen ions increases.
Failure in the tenth to fifteenth repetition
After 30 seconds of operation, and this is approximately 10-12 repetitions, the cause of failure is the complete exhaustion of creatine phosphate and the accumulation of a large number of hydrogen ions. Recovery will last a very long time. With an increase in the number of repetitions, each repeated approach becomes more difficult due to the accumulation of hydrogen ions, and hydrogen ions do not quickly leave the cell (from two minutes to an hour).
Work over 15-20 repetitions (40 seconds of active work) is of no interest from the point of view of strength training, as strong catabolism begins in the muscles due to the high concentration of hydrogen ions, which themselves destroy the cell. And besides, lysosomes are activated, which inside the cell begin to “eat” the injured protein structures.
The criterion for assessing the strongest accumulation of hydrogen ions is a strong muscle burning sensation, due to which, in general, one has to stop the exercise. And if, for example, you did 20 repetitions of squats, and failure was a lack of strength, then this is not so critical.