- 27 April 2018
- Posted by: Eva Galaz
- Category: Uncategorized
The scientific literature states that physical exercise is capable of inducing profound changes in the activity of the neuroendocrine and metabolic system.
The first mechanism that is established in response to a training stimulus is the activation of the adrenal medulla and the posterior lobe of the pituitary gland. In this phase, defined autonomous, there is the release of catecholamines, adrenaline, noradrenaline and vasopressin (ADH). This phase is caused by the activation of the sympathetic nervous system and takes place in a few seconds. In a slower way, instead, the adenohypophyseal hormonal response is achieved, which is then framed in a subsequent defined metabolic phase.
The studies carried out on brain activity have shown that the marathon runners, practicing a long distance running activity, can undergo functional brain changes. In these subjects it has been seen that nerve impulses of transmission of the visual system are faster than sedentary subjects. This statement was made possible thanks to the application of the “evoked visual response test” (VER-test). The VER-test shows that in the marathon runners, when resting, the electrical impulses reach the occipital area about 15 thousandths of a second before that in the control subjects. But not all nerve impulses increase, in fact the marathon runners present an extraordinarily slow pulse activity of the medulla oblongata, that is the part of the brain that controls the autonomous functions (heartbeat, breath, vasodilatation).
The effects of modified brain activity are also reflected in the plasma levels of some neurormones (catecholamines and endorphins) that change during long distance travel.
In fact, catecholamine levels increase very significantly during a very long stroke. In an experiment performed during the New York marathon it was shown that the levels of adrenaline and noradranaline increased by 300% up to 10 ° km and remained at these levels up to 30 ° km. At the end of the race catecholamine levels reached 600% compared to the starting values (Fortunio, Moretti, 1985). The literature on the subject states that norepinephrine levels rise gradually as labor intensity increases and become disproportionately high for very intense exercises, while adrenaline rises considerably during heavy exercises. The training of a marathon runner induces a series of variations that make the athlete less excitable as a result of physical effort and therefore more suitable for performance.
The marathon runner is also characterized by the presence of high levels of beta-endorphins, ie an endogenous opioid involved in the mechanisms regulating pain behavior and control. Among the effects on behavior we remember the direct influence on the mood and on the sleep / wake mechanism. In particular, the marathon runners are defined as “obliged runners”, when they have a fairly common personality, ie they manage to dominate the sense of hunger, endure physical fatigue and pain, refuse to be sick and have a tendency to instability emotional. This leads them, in case of interruption of training for reasons independent from them, to what has been defined by American scholars as the “exercise deprivation syndrome”. In fact, the marathoner, in these situations, shows strong changes in mood and has a tendency towards depression. Probably the elevated levels of this hormone are a biochemical basis that can explain the slowing of the activity of the medulla oblongata that involves a greater control and a reduction of the respiratory and circulatory frequency and of the mechanism of vasodilation.
The most characteristic and ever-present aspect of adaptation syndrome is the appearance of hypertrophy of the adrenal cortex. This is a consequence of the stress induced by prolonged exercise, which leads the body to react by increasing the supply of corticoids, especially glycocorticoids. Probably the increased requirement of the organism of corticoids is the element that stimulates the hypophysis to a hyperincrement of corticotropic hormone with consequent hypertrophy of the adrenal cortex. The response from the adrenal cortex after an intense physical activity can be assessed through the dosage of cortisol, 18-hydroxy-deoxycorticosterone (18-OH-DOC), aldosterone and dehydroepiandesterone sulfate (DEA-S). Following prolonged exercise, an increase in all plasma levels of these hormones is noted. One of the most important is undoubtedly the cortisol that exerts important actions on the metabolism including the increase of glucose production from non carbohydrate material, through the process that is called “gluconeogenesis”. This hormone not only directly accelerates the hepatic share of neoglicogenesis, but indirectly increases the biosynthetic capacity of this pathway, thus favoring the synthesis of various enzymes involved in this process. To be able to sustain this increased neoglicogenesis, cortisol stimulates the demolition of proteins in amino acids, especially in skeletal muscle. Its regulation and circulation is regulated by the adrenocorticotropic hormone (ACTH). There are numerous testimonies on the increase of cortisol following the activity carried out by a marathon runner, the basic assumption is that the exercises are carried out for a duration of more than 20 minutes and with an intensity of not less than 60% of the VO2 max ( Fortunio, Moretti, 1985). Moreover, the maximum increase occurs in the 30 minutes following the end of the effort.
An exercise carried out for a long time also produces an adaptation to the level of thyroid hormones. Just the scholar Refsum has stated, based on experiments carried out in Norway, that following an intense activity of resistance over long duration (marathon), there were significant variations in the concentrations of triiodothyronine (T3) and thyroxine (T4) and their return at baseline levels it only occurred after several days of recovery. These two hormones are essential for proper metabolism and normal cellular function and act on all cells of the body allowing proper functioning of the brain, cardiovascular system, muscle, protein synthesis and glucose and lipid metabolism. The increase in these hormones usually occurs at the end of prolonged exercise, probably because initially there is a consumption of T3 and T4 stored inside the thyroid gland, but without creating the toxic effects that are reported in cases of hyperthyroidism.