As discussed previously, your body only has so much glycogen that it can store and you should be trying to utilize as much fat for energy as you can. When your body no longer has glycogen, which is a stored form of carbohydrates, you are no longer able to burn fat and your primary source of energy is gone. At the point where your stored glycogen has been entirely depleted and you can no longer consume enough carbohydrates to create more glycogen, you hit the wall. Ways to Prevent Injury Gradually increase your weekly mileage and the distance of your long run. Make sure your running shoes are designed for your feet and long distance training.
Most running stores have shoe experts.
Listen to your body. If you have a nagging pain that does not go away, take some time off or consult a physician. Orthopedists, Podiatrists and Sports Medicine physicians are trained to handle many issues related specifically to running. Get the additional sleep and nutrients your body needs. Take at least a day off each week to let your body recover from the rigors of running.