[Biochemical mechanisms of skeletal muscle adaptation to increased activity]

The adaptation changes caused by the systematic muscular activity relate to morphology and functional properties of the muscular fibre subcellular structures, content and state of substrates and enzymes. There occurs not only an increase in the activity of enzymes but also a change in the ratio of the activities in polyenzymic systems. The increase in the enzymes activity is based on the substrate induction and derepression of the enzymes synthesis as well as changes in the isoenzymic spectra, sensitivity of the enzymic systems to hormones. All these changes are specific and determined by the functional profile of the muscles and character of the muscular activity. The energy supply of the adaptive synthesis of structural and enzymatic proteins, phospholipids and a more intensified synthesis of different substrates (glycogen, phosphocreatine) is based on regular changes occurring at rest determined by muscular activity and providing for a higher energy production during this period. Development and stabilization of the adaptation biochemical changes is under control of the chemical self-regulation of the metabolic cycles, neuro-trophic--somatic and sympathetic as well as of the endocrine regulation. At the different stages of adaptation its biochemical mechanisms have definite differences.