Imagine standing with your bare feet on the ground. In this natural position the feet are level and there is no difference between the height of the heel and forefoot. When running barefoot (or naturally) the foot will instinctively land on the forefoot rather than the heel. This forefoot landing causes less impact than heel striking as it uses the natural cushioning of the foot and leg. The body's center of gravity moves forward, cadence increases and there is no loss in momentum.
Our footwear is designed around this natural movement. They keep the foot close to the ground so that it can do what it does best. Over the last 30 years a process for selling supportive, heavily cushioned running shoes has developed. Yet, injury rates amongst runners are unchanged. Natural running has been associated with a reduced likelihood of injury and increased speed and efficiency.