He did not give any names of athletes, and the BBC's Tom Burridge in Madrid says the trial is unlikely to shed light on doping beyond the world of cycling.
Since 2004, when doping allegations against Armstrong first came to light in a book by French sports journalist Pierre Ballester, the foundation has experienced steady year-to-year revenue growth, according to financial records, with the exception of a dip from 2005 to 2006, the year Armstrong was cleared of allegations stemming from a 1999 drug test.