Effects of anaemia and stepwise-induced polycythaemia on maximal aerobic power in individuals with high and low haemoglobin concentrations

Increasing the haemoglobin concentration (Hb]) improves the oxygen transport capacity but it also increases the viscosity of the blood. The influence of changes in Hb] and viscosity on submaximal exercise capacity and maximal aerobic power was investigated in eight healthy males in varying states of training and with a normal resting Hb] (Hb]_r), ranging from 123 to 178 g]^-1. The subjects were venesected five times (450 ml per unit) and exercise tests were performed in the anaemic state. After 5–7 weeks, when Hb] had returned to the ‘normal’ value, a stepwise re-transfusion of three to five units of blood was performed with exercise tests after each transfusion. The Hb]_r was 137 ± 15 g l^-1 in the anaemic state (A) and 170 ± 16 g l^-1 after the last re-transfusion (LT). The V_o2max rose from 3.94 ± 0.35 in A to 4.68 ± 0.30 1 min^-1 after LT. Individual regression lines for Hb] and V_o2max revealed a mean increase in V_o2max of 19 ± 6 ml min^-1 per g l^-1 change in Hb]. This value did not differ between individuals with high and low normal Hb]. Furthermore, in intra-individual comparisons the relationship between Hb] and V_o2max in high and low individual Hb] ranges was not found to be statistically different despite a 40% increase in the in vitro viscosity from the anaemic to the polycythaemic state. The average individual correlation (based on five to seven measurements) between Hb] at rest and after exercise and V_o2max was r= 0.89 (P > 0.01) in the former case and r= 0.92 (P > 0.01) in the latter. The running velocity corresponding to a blood lactate concentration of 4 mM (V_Hla4.0) increased from 15.3 ± 2.3 in the control state to 15.6±2.3 km h¹ after the last transfusion (P > 0.01). A leftward shift of the blood lactate curve, expressed as a percentage of V_o2max, was found. In conclusion, the results obtained indicate a close relationship between V_o2max and Hb] up to at least 170 g l^-1. Furthermore, both inter-and intra-individual comparisons suggest that the influence of viscosity as such on V_o2max does not differ at high and low Hb] levels.