More than running, it's the way we run that matters and builds us up. Acquiring a forefoot stride, known as the ‘natural’ or ‘mid-foot’ stride, is a long process during which the body undergoes a slow transformation. It's a time of adaptation, combined with an adjustment of movement patterns to improve cushioning with each stride, but also, by transfer, the body's dynamics from everyday life to sport (responsiveness, tonicity...), right up to locomotor ease in senior citizens. In this respect, this stride is a therapy that is part and parcel of a new art of running. But running economy is not only based on technique, it also depends on posture and, more specifically, in the context of this book, on the freedom and balance of the pelvis, the suppleness and elasticity of the thorax, the strength of the back muscles and the solidity of the trunk - all elements that are developed through quadrupedal exercises or climbing and that improve the dynamics of running.