For every physical activity, the body requires energy. The amount of energy needed depends on the duration and type of activity. Energy is obtained from the body stores or from the food we eat. Glycogen is the main source of fuel used by the muscles to enable you to undertake both aerobic and anaerobic exercise. If you train with low glycogen stores you will feel constantly tired, your training performance will be lower, and you will be more prone to injury and illness. For this reason, we will consider what glycogen is and how your diet can positively impact your performance and recovery during and after exertion.