Energy Systems: ATP (Adenosine Triphosphate

Energy Systems: ATP (Adenosine Triphosphate)

Energy Systems

Energy Systems ATP (adenosine triphosphate) is the only usable form of energy for muscle contraction. It is a molecule made up of a nitrogenous base (adenine), a five-carbon monosaccharide, pentose, and three phosphates.

 

Because the concentration of ATP in the human organism is very low (5x10-6mol.g-1), it only reaches approximately 0.5 seconds of intense muscular contraction, due to this, the existence of different energy systems that are in charge is essential. to perform the replacement of ATP to prolong muscle activity. The three existing energy systems are a) Alactic Anaerobic System, b) Lactic Anaerobic System, and c) Aerobic System.

Operation of Energy Systems

The three energy systems function as an energy continuum. This can be defined as the ability of the body to simultaneously keep the three energy systems active at all times, but giving predominance to one of them over the rest according to:

 

• Duration of the Exercise.
• The intensity of Muscle Contraction.
• Amount of Substrates Stored.

Therefore, it should be clear that energy systems are far from functioning as isolated compartments with no relation to each other. Rather, they are operating in continuous interaction, therefore it should always be spoken of a predominance of an energy system over the rest and never of exclusivity in the way of energy contribution for the realization of a certain physical activity.

Alactic Anaerobic System

One of the main considerations regarding this energy system lies in a remarkable characteristic that is its high degree of localization, which is given by its fuel the PCR that is specifically reserved and only within the muscle fibers. This means that it is only stimulated with the particular work of each muscle and that the improvement of this will not cause changes in other muscles not involved in the contraction.

PCR is made up of an amino acid that is creatine linked by a high-energy bond of 10 Kcal. to a match.

PCR: ATP

This amino acid can normally be ingested in the diet in small amounts through the ingestion of meat and fish, or it can be synthesized endogenously through different precursor amino acids that are arginine, glycine, and methionine in the liver, kidney, and pancreas (Kreider 98). The concentration of PCR in skeletal muscle fiber is 3 to 5 times higher than the concentration of ATP (15x10-6.g-1 from muscle).

ENZYMATIC REACTION

Once the breakdown of ATP for the production of mechanical energy begins (remember that it only lasts up to 0.5 seconds of intense muscle contraction), the phosphorylation of this substrate is produced mainly by PCR, in which the high-energy bond is destroyed. by the action of creatine kinase, separating creatine on the one hand and phosphorus on the other. The chemical energy contained in the high-energy bond is released into the environment to produce the phosphorus binding of phosphocreatine to ADP to obtain new ATP.

DYNAMICS OF ATP RESTITUTION FROM PCR

In very high-intensity exercises, the PC-ATP system is the one that produces the fastest phosphorylation of ATP, this is because PCR is stored in the cytosol very close to the sites of ENERGY use, and because the hydrolysis of the PCR produced by creatine kinase is rapidly activated by the accumulation of ADP and we must carry out several enzymatic reactions (only one) before the energy is transferred to supply the replacement of ATP. On the other hand, an inhibitory factor for this enzyme is the decrease in pH, which can be caused by an increased accumulation of lactic acid.

In the following graph taken from Willmore (97), it can be seen how the concentrations of ATP and PCR vary during a period of intense muscle contraction. The interesting thing to note is that beyond the PCR concentrations reaching really low levels, the ATP concentration is still very high, when the PCR concentration has dropped to 10% of its initial content, the ATP concentration is 90% approximately (Chicharro-Vaquero 98). Another interesting issue to note is that after four seconds of muscular work the PCR has been depleted by 80%.

SYSTEM CAPACITY

The possibility of maintaining a high degree of phosphorylation of ADP from the phosphocreatine system lasts a period that is very short, approximately between 8 and 10 seconds, during which time this energy system predominates over the other two in the route of energy intake. This is because reaching 8-10 "of intense contraction, PCR reserves are practically depleted since there is no possibility of PCR replacement during muscular activity, since it is carried out during the pause.

PHOSPHOCREATINE RESYNTHESIS

To carry out the resynthesis of PCR, the provision of energy provided by ATP is also necessary, which is sustained by the other two energy systems, the lactic anaerobic system, but mainly the aerobic system. About the latter, a shortening of the PCR resynthesis time has been found in endurance runners, reflecting a better oxidative capacity of their muscles (Chicharro -Vaquero 98). In general, there is a significant correlation between PCR resynthesis time and VO2 max. The latter prioritizes the importance of aerobic training within sports where intermittent explosive gestures are decisive for sports performance (soccer, basketball, rugby, etc.).

The following table shows the different PCR restitution percentages at different pause times. As can be seen in the first 30 "of it, 50% of the PCR is restored, this is the so-called fast PCR restoration phase, and in the next 2 min. 30 seconds, 48% of which are part is restored. of the slow phase.

METHODOLOGICAL CONSIDERATIONS ABOUT THE STIMULATION OF THE PC-ATP SYSTEM

Different methodological guidelines are set out below, to be taken into account when training on explosive sports gestures that demand high phosphagen activity.

a) That the work intensities are maximum or supramaximal, due to neuromuscular stimulation and the massive recruitment of explosive fibers. 

b) Considering that this is a local energy system, the increases in the levels of PCR and enzymes would occur mainly in the stimulated muscle fibers, therefore exercises should be performed as similar as possible to the specific competitive gestures, within this point is It is pertinent to bear in mind that there are also positive neural adaptations that help to increase power, strength, and speed.

c) That the muscular system is well warmed up but without any previous fatigue, therefore it is advisable to carry out explosive type workouts after the warm-up and before any type of stimulus, be they lactic or aerobic, technical, tactical, etc.

 d) That the stimuli are alactic because when the concentrations of lactic acid are increased, decreases in the pH occur that inhibit the action of creatine-phospho-kinase. Lactic acid also produces an inhibition of explosive muscle fibers and in coordination with the consequent alteration of sports techniques.

 To avoid the accumulation of lactic acid mentioned in the last point, the density of the stimulus must be taken into account, which is constituted by the duration of the exercise, which should not be greater than 8-10 "in duration because exceeding these times, PCR reserves are almost nil and anaerobic glycolysis is notably activated. And secondly, due to the pause of exercise, which must guarantee sufficient PCR restitution, to start work again, otherwise in the next series the concentration of lactic acid. Below are several practical examples of various muscle power and speed training stimuli.

1) Reaction Speed

Exercises that are executed at very high speed, based on various stimuli (visual, auditory, tactile, etc.). The duration of the post-stimulus work should be extremely short, less than 2 "in duration, and highly explosive. Stimuli can be distributed in 3 sets of 4 repetitions with a 20 to 30-second micro-pause, and the duration of the pause between sets of 1 minute, time that can be used to explain the next exercise.

2) Acceleration Speed

Speed passes at the maximum intensity of between 10 and 30 meters. Of course, the selection of the distance will vary according to the sports specialty in question.

 

EXAMPLES