Adaptation to Submaximal Physical Training

Submaximal training can induce adaptational changes in the skeletal muscles, cardiovascular system, respiratory system, endocrine system, etc. Knowledge of the signs of adaptation and its magnitude, the factors causing it, as well as an awareness of the significance of the adaptation for the improvement of physical capacity to exercise is essential to develop an optimal training programme and with an adequate recovery process to achieve the maximum positive effect with the minimum negative effect on the athlete’s health. Body adaptation resulting from regular aerobic training can involve adaptation of the muscle enzyme systems, changes in the vascularization and type characteristic of muscle fibers, metabolic changes in the trained muscles and muscle groups related to the glucose utilization and the use of glycogen and fats as sources of energy, changes in the blood, the immune and coagulation status of the body, as well as changes in the parameters of aerobic working capacity of the organism. Regular submaximal exercises have been found to increase the activity of key oxidative enzymes in the metabolic pathway for the breakdown of carbohydrates hexokinase (HK) and citrate synthase (CS) and fats – 3-hydroxyacyl-CoA dehydrogenase (3-HAD) and carnitine palmitoyltransferase (CPT) and in the respiratory chain citochrome c oxidase (CCO). Submaximal training induces vascularization in the muscles containing predominantly oxidative muscle fibers. The muscle fibers in the groups of muscles trained submaximally can even undergo a type transformation. The insulin-mediated glucose transport in the cells of the recruited muscles is selectively increased. A metabolic adaptation occurs as the body shifts from using carbohydrates for energy to using fats; the subsequent “glycogen-sparing” effect enhances the working capacity. Permanent changes occur in the humoral immunity evidenced by the increase of the serum IgA and IgG concentrations. The system of oxygen transport in the blood adjusts to more economical operation. As a final result both the external system of oxygen delivery and the mitochondrial system of oxygen utilization undergo adaptation which leads to a moderate increase of maximal oxygen consumption, but greater increase of the oxygen running economy.