[Reaction of the cardiovascular system to static load after changes in body position].

Cardiovascular responses of healthy male subjects to static loading in the horizontal, orthostatic and antiorthostatic positions were investigated. The body position was found to affect significantly both the sign and magnitude of circulation parameters. It was also shown that static loading tolerance was lower in the orthostatic than in the antiorthostatic position. It was hypothesized that the complex mechanism of adaptation to static loading involves purely physical factors (obstruction of small arterial vessels and blood discharge from veins of the strained muscle), central, intermediate and local reflex mechanisms. Resistance vessels play a predominant role in limiting systemic arterial pressure in the orthostatic position. Of greated importance in the horizontal position is venous blood pooling limiting its return to the heart. Rearrangement in hemodynamics during static loading is accompanied by an increase in the effective coronary blood flow which is the greatest in the orthostatic position.