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 o2 max 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 o2 max revealed a mean increase in V o2 max 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 o2 max 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 o2 max 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 h 1 after the last transfusion ( P > 0.01). A leftward shift of the blood lactate curve, expressed as a percentage of V o2 max , was found. In conclusion, the results obtained indicate a close relationship between V o2 max 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 o2 max does not differ at high and low Hb levels.