As stated, walks are very good and important for his good health. It's also a great bonding tool for you both. Is there other YT'ers near enough to do some play dates with? A dog park? Doggie Daycare where he can run and interact with others. Boo doesn't play with toys either, but he will "rough-house" with DH, and play with other dogs. (but not the sister so much
girl cooties!!) And we have a backyard that he will run around in. Be creative, look outside the box for ways to get him moving. Even if it's a slow walk to start with, the benefits are there.