Shin splints and other injuries which are caused by the consistent compact when running on hard ground.  They can cause immense pain and it very often means that exercising must cease immediately until the shin splints have settled down and the swelling has subsided. Nike Trainers have invented a new trainer to counteract the effects of shin splints and have proved to be highly effective in tests conducted by runners of all levels from novices to the more experienced marathon runner both of which suffer from shin splints.  They are also very reasonably priced considering the technology that has been used to develop these trainers.