before the race... if the trainer or jockeys speaking to u.. and u have an option to choose yes or no...
well... that's a challenge thrown to u...
for example, a jockey or trainer will challenge u in one of the race which u and him are in....
so u press the 'triangle' button to view yours and his horse... u do the studies between both horse and u decide if u want to take the challenge..
so far, i don't see much happening when i won the challenge.