DSD rules; Differences of Sexual Development. As I understand it, the two Namibian athletes have higher than normal levels of testosterone and for reasons that are beyond me, have been moved to the 200 metres rather than running the 400 metres.
It has been posited that the 'endurance sprint' events (400/800/1500) are those in which the advantage is most pronounced so the ban only applies there. It's a mess, obviously.
What are these new rules the commentators keep referencing but not explaining about runners dropping down from 400m to 200m?