The 18 listed directors of USA Gymnastics were facing calls to resign after disgraced team doctor Larry Nassar was sentenced to up to 175 years in prison for abusing young female gymnasts who were entrusted to his care.After Nassar was sentenced on Wednesday, the chief executive of the US Olympic Committee called for all current USA Gymnastics directors to step down.Piling pressure on the directors, the president of Michigan State University, where Nassar had also worked, decided on Wednesday to resign after facing a barrage of criticism for not doing enough to halt the abuse."All current USA Gymnastics directors must resign," US Olympic Committee Chief Executive Scott Blackmun said in an open letter on Wednesday.The USOC decided not to decertify USA Gymnastics as a national governing body because such a move would hurt clubs and athletes who had no hand in the scandal, he said.USA Gymnastics did not respond directly to the calls for mass resignations. In a statement on Wednesday, it said the sport "may be better served by moving forward with meaningful change within our organization, rather than decertification."Three USAG board members resigned on Monday in the wake of the scandal, following the exit last March of the federation's president and chief executive.But former US Olympic gymnasts abused by Nassar and the USOC chief executive have said a full change in leadership must be implemented.As his victims wept in a Michigan courtroom on Wednesday, long-time USA Gymnastics team doctor Nassar was sentenced to up to 175 years in prison for abusing young female gymnasts who were entrusted to his care."I've signed your death warrant," Ingham County Circuit Court Judge Rosemarie Aquilina told Nassar, following days of accounts from about 160 of his victims.