I found a reference to Treibball when looking at the schedule for the upcoming pet show in St. Charles, Illinois. Since I didn't have a clue, I Googled the word and found it refers to a game played in Germany that involves herding exercise balls into a goalie's net. There are numerous videos on YouTube--most in German. However, Living with Dogs has several YouTube videos in English that show how to begin training. They also offer a book translated from German, Treibballing Handbook.
From watching the German videos, treibballing looks like an excellent way to exercise your dog's body and mind and to increase the handler-dog working bond.
Dusty is a reactive, over-the-top dog who gets very excited in the presence of large balls. I took him out and worked on sending him to a mat, which is step one. I was really shocked that he was able to go to a mat and lie down. I didn't think I had taught him that behavior, but apparently I did. (Either that or he learned from watching me teach it to other dogs.)
The next step was to bring out the pig ball. (It's a hard plastic ball about 18" in diameter that was designed to keep pigs from getting bored.) Dusty goes ape over this ball, and I very rarely let him play with it. While straddling the ball, I sent Dusty to his mat. He was able to do it, but it was hard for him to ignore the ball. When released to his reward, he lunged at the ball several times. If Dusty can learn to do this new sport, it may prove to be transforming experience as far as his general reactivity and self-control are concerned.