MITOCHONDRIA: power generators prendendo spunto da una curiosità di Maxrunner, con molta calma mi sono messo alla ricerca di come l'attività di resistenza possa influenzare il livello di mitocondri nei nostri muscoli.
ebbene:
I MITOCONDRI NON SONO DETERMINATI GENETICAMENTE MA POSSONO ESSERE MODIFICATI IN NUMERO, DIMENSIONE E PRODUTTIVITA' CON OPPORTUNI ALLENAMENTI
Quando una cellula assume energia dall’ambiente che la circonda, tale energia si trova sotto forma di energia chimica contenuta nelle molecole di cibo (es. glucosio) o sotto forma di energia luminosa. Tali tipologie di energia devono essere convertite in forme che possano essere meglio utilizzate dalle cellule. Alcuni di questi processi di conversione avvengono nei mitocondri; la forma in cui generalmente viene convertita l’energia è l’ATP.
I mitocondri sono organuli complessi nei quali avviene la respirazione aerobica, un processo che richiede ossigeno e che consiste in una serie di reazioni che trasformano l’energia chimica presente nel Cibo in ATP. Durante la respirazione aerobica atoms of oxygen and carbon are removed from food molecules, like glucose, and converted to carbon dioxide and water. Mitochondria are more numerous in the cells are very active, requiring large amounts of energy. Each mitochondrion is composed of a double membrane that gives rise to two distinct compartments: the intermembrane space, which is formed between the inner and outer membranes, and the matrix, which is surrounded by the inner membrane compartment and contains enzymes that degrade food molecules and convert their energy into other forms of chemical energy.
The electrons produced by the reduction reactions of glucose and glycolysis through the stages of formation of acetyl CoA and the citric acid cycle are transferred by molecules called acceptors (NAD and FAD) to form NADH and FADH. These components enter the electron transport chain, here the electrons to high energy of their hydrogen atoms are transferred from one acceptor to another. Such transfers are done through a series of reactions that have as a final product the production of ATP. This process of ATP production is called oxidative phosphorylation. The electron transport system consists of a chain of electron acceptors, which is located in the inner mitochondrial membrane.
In terms of production yield of ATP, oxidative phosphorylation (which occurs in the mitochondria) is significantly higher than direct oxidation (glycolysis and the citric acid cycle) of glucose. In fact, in oxidative phosphorylation to produce 32-34 molecules of ATP per molecule of glucose, compared with 4 molecules of ATP produced by oxidation of the substrate glucose.
is therefore important, in endurance sports, where most energy is supplied via aerobic metabolism (oxidative phosphorylation), the muscles involved with a good component and high mitochondrial enzyme activity within individual muscle cells.
Skeletal muscle has the ability to undergo major adjustments in response to training. The activity of resistance increases the capacity of aerobic muscle metabolism that is mediated by an increase in mitochondrial hypertrophy with no increase in muscle strength. To assess the possibility that variations in mitochondrial content in the muscles are due to physical exercise, rather than genetically mediated, several studies have been conducted on animals that have undergone training through a program running on a treadmill with a progressive increase of duration and speed, kept for 12 weeks. Since this program was increased by approximately 2-fold in muscle capacity to oxidize pyruvate, fatty acids and ketone bodies. The mitochondria present in muscle which to exercise exhibited an increase in the reactions of oxidative phosphorylation exhibit increased ability to generate ATP. The increased capacity to generate ATP through oxidative metabolism is mediated by the increase in the level of mitochondrial enzymes that catalyze the oxidation of fatty acids (FFA), the citric acid cycle, respiratory chain and ATP synthesis. Me electron microscopy studies have shown that increasing the size and number of mitochondria are involved in adapting all types of muscle fibers undergo training sheets are subject to adaptive processes.
The endurance exercise induces an increase in mitochondria and consequently increases the ability of muscle to generate ATP through oxidative phosphorylation. The increase in mitochondria leads to a reduction in organ homeostasis during exercise at sub ceilings, as evidenced by a smaller reduction of creatine phosphate and ATP, reduced increase of ADP, AMP, phosphate and lactate, reduced and increased glycogenolysis ability to resist fatigue. There are also changes on the use of energy substrate, a decrease of glucose and glycogen in favor of an increased use of fat.
When a muscle contracts the ATP is used with no loss of creatine phosphate and of itself, as opposed you is an increase in the concentration of ADP, Pi (inorganic phosphate) and AMP. The electron transport in mitochondria is coupled to the synthesis of ATP and is limited by the availability of ADP. The balance in the concentration of ADP, ATP and P that occurs during exercise at sub maximum is determined by muscle work and the quantity of mitochondrial muscles themselves. During the year the concentration of ATP decreases and that of ADP and P increases until the respiratory chain is sufficiently activated to provide ATP through oxidative phosphorylation and thus balance the rate of ATP used in muscle contraction. As a result of the increase in mitochondria, the consumption oxygen and production of ATP to mitochondria are more efficient in the target muscle. In a few words with multiple mitochondrial respiratory chain and ATP concentrations decreased PC less, while ADP, AMP and P increases to lower levels of steady-state muscle in trained than untrained.
From this we can conclude that the endurance sports, at the sub ceilings trigger a series of adaptive processes in the body that better compensate for the increased demand of energy for muscle contraction.
The increased number of mitochondria and the increase of enzyme catalysts for the reactions of oxidative phosphorylation consent to muscle to maintain a long relationship ATP / ADP at levels sufficient to allow the muscle to contract repeatedly for longer periods. An increase in mitochondria can increase the threshold level of sub maximal exercise, providing the muscle to increased synthesis of ATP. Finally, after a workout geared towards stimulating the resistance, due to an increase in number and activity of mitochondria, to generate a greater ability to use organic fatty acids as energy substrate, sub ceilings for levels of activity.
