The aim of this study was to test the hypothesis that
post-exercise hypotension was the mechanism for the plasma volume and
albumin gain during recovery. Seven healthy young men completed two experiments (> or =1 week apart) to exercise continuously at 65% of peak aerobic capacity for 60 min followed by the recovery without (experiment 1) or with
phenylephrine infusion (experiment 2) to counteract
post-exercise hypotension. Heart rate, arterial pressure (Finapres), plasma volume (PV,
Evans blue dye dilution), haematocrit, haemoglobin, plasma total solutes (refractometer),
albumin, total
proteins (colorimetric method), [Na+] and [K+] were not different prior to the experiments. Exercise decreased PV -13.7% (-521 mL) and -14.2% (-566 mL) at the end of 60 min in experiments 1 and 2, respectively, associated with increases in the concentrations of
plasma albumin, total
protein and solutes. These changes were similar between the two experiments. Following 30 min recovery in experiment 1 the decreased PV was not significantly different from the baseline. Although the volume restoration was complete at the end of 90 min recovery, the change in the
albumin concentration was still above zero, indicating a gain of 11 g
albumin (P < 0.05). When
phenylephrine was infused during recovery, there was no gain in intravascular
albumin associated with a sustained decrease in PV (-7% or -280 mL, P < 0.05) observed at the end of experiment 2. These data suggest that
post-exercise hypotension may be the mechanism for a gain of intravascular
albumin via the lymph return, which enhances plasma water retention and PV restoration during recovery from exercise induced hypovolaemia, even without
rehydration.