Strategies of adaptation of small arteries in diaphragm and gastrocnemius muscle to aerobic exercise training

Aerobic exercise training is associated with adaptive changes in skeletal muscles and their vascular bed; such changes in individual muscles may vary depending on their characteristics and recruitment. This study was aimed at comparing the effects of eight-week treadmill training on the locomotor and respiratory muscles in rats. The training course increased the aerobic performance in rats, which was evidenced by an increase in maximum O₂ consumption and a decrease in the blood lactate concentration in ramp test. The succinate dehydrogenase activity was increased in the red portion of the gastrocnemius muscle, but not in the diaphragm of trained rats. Arterial segments were isolated from feed arteries and studied by wire myography. The relaxation in response to acetylcholine in gastrocnemius arteries in trained animals was higher as compared with controls (due to higher NO production), while contractile responses to noradrenaline (in the presence of propranolol) were not changed. On the contrary, the endothelial function of diaphragm arteries was not affected by training, but contractile responses to activation of α-adrenoceptors were markedly increased. Thus, aerobic training may increase the blood supply rate to both locomotor and respiratory muscles, but the underlying regulatory mechanisms are different. The results obtained allow us to reveal the physiological mechanisms that determine the physical performance of the body under conditions of compromised functioning of the respiratory system.