Induced hypervolemia, cardiac function, VO2max, and performance of elite cyclists

Objective: To determine whether plasma volume expansion (PVexp) in elite endurance-trained (ET) cyclists, who already possess both a high blood volume (BV) and a high (V) over dot O-2max leads to further enhancements in their cardiac function, (V) over dot O-2max,and endurance performance (time to exhaustion at 95% (V) over dot O-2max). Methods: Nine male ET cyclists (V) over dot O-2max = 65.9 +/- 0.6 (SEM) mL.kg(-1).min(-1)) were studied employing a double blind, cross-over design; i) before PVexp, ii) after sham PVexp (Sham), iii) after restoration of normocythemia, iv) after PVexp (6% dextran), and v) upon reestablishment of normocythemia. Results: PVesp resulted in a 537 +/- 61 mL increase in BV (P < 0.05). Maximal cardiac output and maximal stroke volume were higher (P < 0.05) after PVexp, but the magnitude of these increases was only sufficient to counter the hemodilution effect (lowered O-2 content) of PVesp. such that O-2 transport, (V) over dot>O-2max, and endurance performance remained unchanged. Conclusions: Expansion of BV in elite ET cyclists, who already possess a high BV, does not improve their (V) over dot O-2max and endurance performance. Elite ET athletes may already be at an optimal BV, which is at or near the limits of their diastolic reserve capacity.