Secrets of blood test for Olympic athletes. Why blood test is important for better performance. In this video, I would like to talk about why it is important for athletes to do blood tests and what kind of samples they need.Olympic athletes all have to take a blood test before their events, so they can find out if they're getting enough vitamins and minerals. The secret of these tests is that they don't have to wait until the event to know what they need. This video will teach you what y...