Importance of post-exercise hypotension in plasma volume restoration

The aim of this study was to test the hypothesis that post-exercise hypoten sion was the mechanism for the plasma volume and albumin gain during recove ry. Seven healthy young men completed two experiments (greater than or equa l to 1 week apart) to exercise continuously at 65% of peak aerobic capacity for 60 min followed by the recovery without (experiment 1) or with phenyle phrine infusion (experiment 2) to counteract post-exercise hypotension. Hea rt rate, arterial pressure (Finapres), plasma volume (PV, Evans blue dye di lution), haematocrit, haemoglobin, plasma total solutes (refractometer), al bumin, total proteins (colorimetric method), [Na+] and [K+] were not differ ent 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, as sociated with increases in the concentrations of plasma albumin, total prot ein and solutes. These changes were similar between the two experiments. Fo llowing 30 min recovery in experiment 1 the decreased PV was not significan tly different from the baseline. Although the Volume restoration was comple te at the end of 90 min recovery, the change in the albumin concentration w as still above zero, indicating a gain of 11 g albumin (P < 0.05). When phe nylephrine was infused during recovery, there was no gain in intravascular albumin associated with a sustained decrease in PV (-7% or -280 mL, P < 0.0 5) observed at the end of experiment 2. These data suggest that post-exerci se 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 rehydrati on.