Day seven of the World Championships from Berlin is expected to be dominated by the all-American showdown in the men's 400m between Olympic champion LaShawn Merritt and world champion Jeremy Wariner. Current world record-holder Michael Johnson will be on hand to offer his expert opinion from the studio. Elsewhere, American Allyson Felix defends the 200m title she won in Osaka in 2007, with the men's high jump and women's discus competitions also reaching their conclusions. Show less