Krip, B., Gledhill, N., Jamnik, V., & Warburton, D. (1997). Effect of alterations in blood volume on cardiac function during maximal exercise. Medicine and Science in Sports and Exercise, 29, 1469-1476.

The effects of manipulating blood volume on cardiac function in endurance trained (N = 6) and untrained Ss (N = 6) were examined. Both groups were examined in a control condition. The endurance-trained Ss were then evaluated after having blood volume reduced by 500 ml while untrained Ss had blood volume expanded by 500 ml.

In normal circumstances endurance trained athletes had significantly greater blood volume, maximal diastolic filling rate, maximal ventricular emptying rate, stroke volume, cardiac output, and maximum aerobic capacity (VO2max). When blood volumes were manipulated these differences disappeared.

Implication. Changes in stroke volume and cardiac output are attributable to changes in blood volume, which enhances diastolic filling.

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