Apologies for being inactive, needed some sleep . I was going to say so but didn't want to assume I'd won!
The only 3 equestrian sports in the Olympics I can think of would be dressage, jumping and eventing.
It looks a bit like polo, but that isn't modern so...
Also looks like a ball in someone's hand but I can't think what that would be. Any other hints?
Sent via iPF from my iPad2 iOS 5.1.
Edit: mis read the info so ignore what I wrote above.
I'm guessing it's handball on horses? I'm sure it had a much more graceful name than that though?