Influence of acute plasma volume expansion on V̇o2 kinetics, V̇o2peak, and performance during high-intensity cycle exercise

Abstract

The purpose of this study was to examine the influence of acute plasma volume expansion (APVE) on oxygen uptake (V̇o2) kinetics, V̇o2peak, and time to exhaustion during severe-intensity exercise. Eight recreationally active men performed “step” cycle ergometer exercise tests at a work rate requiring 70% of the difference between the gas-exchange threshold and V̇o2max on three occasions: twice as a “control” (Con) and once after intravenous infusion of a plasma volume expander (Gelofusine; 7 ml/kg body mass). Pulmonary gas exchange was measured breath by breath. APVE resulted in a significant reduction in hemoglobin concentration (preinfusion: 16.0 ± 1.0 vs. postinfusion: 14.7 ± 0.8 g/dl; P < 0.001) and hematocrit (preinfusion: 44 ± 2 vs. postinfusion: 41 ± 3%; P < 0.01). Despite this reduction in arterial O2 content, APVE had no effect on V̇o2 kinetics (phase II time constant, Con: 33 ± 15 vs. APVE: 34 ± 12 s; P = 0.74), and actually resulted in an increased V̇o2peak (Con: 3.90 ± 0.56 vs. APVE: 4.12 ± 0.55 l/min; P = 0.006) and time to exhaustion (Con: 365 ± 58 vs. APVE: 424 ± 64 s; P = 0.04). The maximum O2 pulse was also enhanced by the treatment (Con: 21.3 ± 3.4 vs. APVE: 22.7 ± 3.4 ml/beat; P = 0.04). In conclusion, APVE does not alter V̇o2 kinetics but enhances V̇o2peak and exercise tolerance during high-intensity cycle exercise in young recreationally active subjects.