I'm no professional, but...
I recommended this on two forum posts already, but you should totally tie something to like yarn, I'm talking about a long line of yarn, something noisy when it hits the ground, and let him chase it around your yard while he goes after it, shepherds LOVE things that move because of their drive, especially a working line pup, not to mention it's easier on their legs, even a nerf ball like this: http://www.ottoenvironmental.com/con...s-ball-35.jpeg
is absolutely perfect, since you can slip the yarn under and tie it. Because they aren't jumping or anything, you'll see that it's easy on the hips, yet tiring and fun.
I also recommend buying a ChuckIt! One of the best things you can buy, rotate with all 3, do the drive thing (pulling a ball on yarn around) for maybe 5 - 10 minutes, or until he's completely bored out, than rotate to Frisbee for a short while, than start playing for the ChuckIt! For a nice long while. Still energy? Well than, drain your pup by taking him for a short walk. Also, shorten the amount of play time in the heat if you're rotating with 3 activities, don't wanna mess with his hips.
I also recommend taking him to at least a big enclosed area with all grass, and just start throwing the ChuckIt! too.
It's good that you're throwing in training though, mental and physical activity works wonders with each other.
Good luck, I'd offer more advice for draining his energy, but my pup has always been low to medium, and acts like the common house cat, rather than a dog.