Scientific studies point us in very interesting directions. First, different surfaces allow for various running techniques based on hardness, degree of unevenness and differences in surface heights. Flat surfaces such as roads, running tracks or treadmills force us into repetitive movements, which in turn cause the repetition of biomechanical imperfections. Running on a soft surface (as compared to a hard surface) does not lead to more injuries, provided the body is used to it.
Additionally, the variation of biomechanical components used when running on natural irregular surfaces brings about a variety of tissue stresses which reduces the risk of overuse injuries. The best running surface is the cross-country-type surface, that is, a firm and irregular surface that allows for a wide variety of lower-body movements and efforts. Since more body parts are being engaged, their adaptation is therefore more significant.