Most full marathoners have hit the “wall” at some point and hence know what it feels like. In scientific terms, the “wall” is when glycogen depletion occurs while running. We store enough carbohydrates in the form of glycogen in our muscles and liver to run about 28 to 30 km and then we hit the wall of glycogen depletion. Our muscles run out of fuel and it really hurts. It slows us down and alters our stride and this is when injuries can happen. Once we get past the wall the pain gets better but doesn’t go away. Once past the “wall” fat burning kicks in, we feel better and our stride improves.