Taking a close look at Synek at 3:30 in http://www.youtube.com/watch?v=DcX7qA3DxdQ and then Knapkova at 0:26 in http://www.youtube.com/watch?v=vJZhlEDlhdY
It looks to me like they are both wearing rowing shorts with a built-in back brace.
All the other sculllers in each race look to be in conventional uni's.
If anyone knows about this Czech kit innovation, I would be grateful for
a) an explanation of how it works and
b) a suggestion about who might be making them