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 l-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 VO2max rose from 3.94 +/- 0.35 in A to 4.68 +/- 0.30 l min-1 after LT. Individual regression lines for [Hb] and VO2max revealed a mean increase in VO2max 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 VO2max 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.(ABSTRACT TRUNCATED AT 250 WORDS)