in the 1970s. But research is now revealing that cushioned running shoes, and the practice of striking the ground heel-first that they encourage, is contributing to running injuries, not preventing them. Before the invention of cushioned running shoes, runners typically adopted a forefoot or midfoot strike. This is the running style the body automatically assumes when its feet are unprotected. In developing countries like Ethiopia, most runners still spend their early years running barefoot or sandaled, and use the same forefoot-strike technique. Research by Harvard professor Daniel Lieberman published in Nature has revealed that the impact force absorbed by the body is considerably higher when heel-strike running, regardless of shoe protection, than when forefoot-strike running. He believes this accounts for the spiralling incidence of repetitive stress injuries among runners today. Despite the promotion of "correcting" running shoes by a multi-billion dollar industry, two million years of evolutionary success as an endurance-running species have given our feet and ankles extraordinary natural shock resistance. The arched structure of the foot and the flexion abilities of the ankle joint work together to absorb the impact of the foot strike while maintaining a natural leg position. This force is then partially returned as the foot propels off the ground. The heel strike, in contrast, transmits impact force straight up the leg to the knee and hips while braking the forward momentum of the runner. As medical research catches up with the biomechanical advantages of "natural running", more and more specialists are advising runners to