A hundred meters after the start they head up the first uphill, starting on the rollerski loop, and shortly transition to grass, dirt, and mud. There are three types of races: short track (roughly 16 minutes), Olympic format (roughly 75-90 minutes), and the 100K marathon. The Olympic format is the most technical of all the races. Along with current and former world champions, all the medal winners from the recent Paris Olympics will be on hand.