In 2016, amid an epidemic of police shootings of African Americans, the celebrated NFL quarterback Colin Kaepernick began a series of quiet protests on the field, refusing to stand during the U.S. national anthem. By "taking a knee," Kaepernick bravely joined a long tradition of American athletes making powerful political statements. This time, however, Kaepernick's simple act spread like wildfire throughout American society, becoming the preeminent symbol of resistance to America's persistent racial inequality. Dave Zirin chronicles "the Kaepernick effect," through interviews with a broad cross-section of professional athletes across many different sports, college stars and high-powered athletic directors, and high school athletes and coaches.

High school -- College -- The pros.