The bigger change for Ledecky in the pool is training on a daily basis against a deep and talented group of male distance swimmers led by Bobby Finke, who matched Ledecky with gold medals in the 800 and 1,500 in Tokyo. (Finke, 22, won the men’s 800 in Greensboro on Wednesday night in a time of 7:54.07). On any given day at practice, Ledecky might line up in the lane next to Finke or Kieran Smith, bronze medalist in Tokyo in the 400 free, and try to match the men lap for lap.