Haemoglobin, blood volume, cardiac function, and aerobic power

Alterations in [Hb], which are mediated through changes in arterial oxygen content, and alterations in BV, which are mediated through changes in cardiac output ((Q) over dot), have a significant effect on both (V) over dotO(2)max and aerobic performance. If BV is held constant, a decrease in [Hb] (anaemia) causes a decrease in (V) over dotO(2)max and aerobic performance, while an increase in [Hb] is held constant, an increase in BV can cause an decrease in both (V) over dotO(2)max and aerobic performance. In addition, an increase in BV can compensate for moderate reductions in [Hb] through increases in (Q) over dot, allowing (V) over dotO(2)max to remain unchanged or even increase. Also, a large portion of the difference in the enhanced cardiovascular function of endurance athletes is due to their high BV and the resultant enhancement of diastolic function. Hence, optimizing both [Hb] and BV is a very important consideration for endurance performance.