V ̇O2max and/or exercise endurance have also been shown to increase in circumstances where [Hb] has been elevated by the administration of recombinant human erythropoietin (rhEPO) to healthy individuals [22,23], athletes [23,24], haemodialysis patients [25,26], and patients with heart failure [27,28], or through the increased Hb synthesis following administration of iron supplements [29]. This evidence concerns the gene GSTM1 and heart failure.