Non-anaemic Fe deficiency (serum ferritin <20.0 μg·L−1, Hb >115 μg·L−1) and anaemia (serum ferritin <12.0 μg·L−1, Hb <115 μg·L−1) are common at all levels of athletic performance and are thought to affect physiological capacity. The gene discussed is GSTM1; the disease is anemia (phenotype).