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 VO2max, leads to further enhancements in their cardiac function, VO2max, and endurance performance (time to exhaustion at 95% VO2max).


METHODS
Nine male ET cyclists (V02max = 68.9 +/- 0.6 (SEM) mL x kg(-1) x 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
PVexp resulted in a 547 +/- 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 O2 content) of PVexp, such that O2 transport, VO2max, and endurance performance remained unchanged.


CONCLUSIONS
Expansion of BV in elite ET cyclists, who already possess a high BV, does not improve their VO2max 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.
Warburton
D E
DE
Kinesiology and Health Science, York University, North York, Ontario, Canada.
Gledhill
N
N
Jamnik
V K
VK
Krip
B
B
Card
N
N
D000328:Adult; D001642:Bicycling / Q000502:physiology*; D001810:Blood Volume / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D013318:Stroke Volume