The best way to tire Gonzo out (and the easiest for me) is to just spray the hose around on the lawn. He races back and fourth biting it, and he will literally chase the jet of water for hours... I think he would die of exhaustion chasing the hose if we let him

Swimming is also the BEST exercise in the summer, because it's no-impact and he loves it more than anything. We throw a tennis ball or his foamy frisbee thing over 100 feet out at our local lake, and he brings it back over and over!