Over the past few years, physicians have been learning more about the long term effects of concussions. Ryan Tierney, a professor of kinesiology at Temple, has been investigating whether some athletes are more prone to developing concussions than others, by testing football and soccer players to see if they had a specific variation of a gene that helps in repairing damaged neurons. "This variation is normal throughout the population, but for people who are going to put themselves in an environment where they are going to receive repetitive head impacts, it becomes more important," Tierney said.