We wanted to determine the influence of total blood volume (BV) and blood lactate quantity on lactate concentrations during incremental exercise. Twenty-six healthy, nonsmoking, heterogeneously trained females (27.5 ± 5.9 ys) performed an incremental cardiopulmonary exercise test on a cycle ergometer during which maximum oxygen uptake (V·O2max), lactate concentrations ([La-]) and hemoglobin concentrations ([Hb]) were determined. Hemoglobin mass and blood volume (BV) were determined using an optimised carbon monoxide-rebreathing method. V·O2max and maximum power (Pmax) ranged between 32 and 62 mL·min-1·kg-1 and 2.3 and 5.5 W·kg-1, respectively. BV ranged between 81 and 121 mL·kg-1 of lean body mass and decreased by 280 ± 115 mL (5.7%, p = 0.001) until Pmax. At Pmax, the [La-] was significantly correlated to the systemic lactate quantity (La-, r = 0.84, p < 0.0001) but also significantly negatively correlated to the BV (r = -0.44, p < 0.05). We calculated that the exercise-induced BV shifts significantly reduced the lactate transport capacity by 10.8% (p < 0.0001). Our results demonstrate that both the total BV and La- have a major influence on the resulting [La-] during dynamic exercise. Moreover, the blood La- transport capacity might be significantly reduced by the shift in plasma volume. We conclude, that the total BV might be another relevant factor in the interpretation of [La-] during a cardio-pulmonary exercise test.
Keywords: erythrocyte volume; hematocrit; hemoglobin concentration; lactate kinetics; performance diagnostics; plasma volume.