Aerobic training led to an isoform shift in lactate dehydrogenase (LDH), with increased expression of LDH-B (isoforms LDH 1 and 2) and decreased expression of LDH-A (isoform LDH 5) in comparison to controls, and decreased expression of monocarboxylate transporter type 1 (MCT1) in an experimental model of breast cancer using the MC4-L2 cell line (229). The gene discussed is LDHA; the disease is breast cancer.