Acute plasma volume expansion: effect on metabolism during submaximal exercise

To examine the effect of acute plasma volume expansion (PVE) on substrate s election during exercise, seven untrained men cycled for 40 min at 72 +/- 2 % peak oxygen uptake ((V)over dot O-2peak) On two occasions. On one occasio n, subjects had their plasma volume expanded by 12 +/- 2% via an intravenou s infusion of the plasma substitute Haemaccel, whereas on the other occasio n no such infusion took place. Muscle samples were obtained before and imme diately after exercise. In addition, heart rate and pulmonary gas and venou s blood samples were obtained throughout exercise. No differences in oxygen uptake or heart rate during exercise mere observed between trials, whereas respiratory exchange ratio, blood glucose, and lactate were unaffected by PVE. Muscle glycogen and lactate concentrations were not different either b efore or after exercise. In addition, there was no difference in total carb ohydrate oxidation between trials (control: 108 +/- 2 g; PVE group: 105 +/- 2 g). Plasma catecholamine levels were not affected by PVE. These data ind icate that substrate metabolism during submaximal exercise in untrained men is unaltered by acute hypervolemia.