Physical exercise is important for your dog, no matter what his age. Just as important though is mental stimulation. Dogs need to be able to exercise their minds too. I am a big fan of not using food bowls and feeding dogs in creative ways which engage their brains. 
Why not take advantage of their need to sniff and forage? Tossing some kibble onto the floor, the backyard deck, the grass or into the crate is a great way to give your dog a job and encourage a natural behaviour.
Some dogs have a stronger need to chew than others. Using food dispensing toys is a great way to feed a meal or two while providing an opportunity to use his mouth in a legitimate way. http://www.sitstaylearn.ca/blog/kong-stuffings-recipes-from-jo-maisey-

Here are some creative ways to provide mental stimulation for your dog. http://www.themoderndogtrainer.net/mental-stimulation-ideas-for-dogs/