Mechanisms of adaptation to physical exertion and the effect of carbon dioxide excess on their formation

4% CO2 addition to normoxic gas medium increased the activity, mass and functional capacity of the left ventricular myocardium, enhanced the stability of acetylcholine (AC) and noradrenaline (NA) storage in the myocardial tissues and stimulated myocardial response to these mediators during physical training of rats (swimming for 2 months). When the duration of the training period was prolonged to 3 months, CO2 had a decreasing effect on the myocardial activity, AC concentration and storage stability, as well as on the myocardial response to AC. The possibility of reducing signal and increasing metabolic CO2 effects during physical training is considered. The importance of intensified heart regulation by sympathetic and parasympathetic mechanisms during adaptation and the role of mechanism dissociation with the decrease in the degree of adaptation are discussed.