Base Training What is it? Base training, is aerobic base building, the foundation of endurance running. It develops your aerobic energy system. Its not fast running, you’re training your body to go further, for longer, with less effort. The aim is to increase mitochondrial density (your cells’ energy factories), strengthen your capillary network (oxygen highways), and improve your ability to burn fat for fuel. In short, you’re teaching your body to become a more efficient engine. Long, steady ru