The effects of an increased step frequency on running economy and injury risk factors during downhill running

Summary Aims Injuries to the lumbopelvic region are often debilitating and result in significant time loss from sports participation. Different factors which have been correlated with the occurrence of injuries are, for example, the magnitude of the anterior pelvic tilt angle and the repetitive impacts the body has with the ground. When running downhill, step length is longer, which translates into a greater joint range of motion, and the vertical velocity at foot contact is greater. As a result, risks of overuse injury could be greater as compared to level running. To help prevent such injuries, we hypothesise that increasing step frequency may be a valid way to reduce the impact with the ground and the maximal anterior pelvic tilt without affecting oxygen consumption, both in level and downhill running. Methods We analysed 10 inexperienced runners at preferred and +10% of step frequency during level and downhill running. We recorded the oxygen uptake together with running kinematics and kinetics. Results When the step frequency was increased by 10%, both in downhill and level running, neither the oxygen uptake nor the running kinetics were modified. In contrast, the maximal anterior pelvic tilt was significantly reduced with increased step frequency. Conclusion For inexperienced runners, these findings show that increasing step frequency may partly reduce the anterior pelvic tilt without significantly influencing the running economy