Short-term immobilization of healthy men: right ventricular function and metabolism during graded exercise

Five healthy male volunteers were subjected to graded exercise tests on a bicycle ergometer (600 kpm/min for 8 minutes) with simultaneous catheterization of the right cardiac ventricle and radial artery, first before immobilization and them after five-day bed rest in the head-down posture (the foot bed end was elevated 4.5 degrees). After immobilization, during exercise the stroke index did not increase, the tachycardia was more marked, the indicators of right ventricular contractility increased [+ max dp/dt, mas (dp/dt) /P, --mas dp/dt], the arterial pressure decreased, and the lactic acid level in mixed venous blood rose. Possible causes of haemodynamic and metabolic alterations, occurring in healthy volunteers during graded exercise following short-term hypokinesis, are discussed.