
I've always used it as per walk. You can also walk him 5 minutes to the park (or wherever) let him run for 5 minutes, sit with him on a bench for half an hour to watch the world go by and see different people, and traffic, give him another 5 minutes running then a 5 minute walk home. It's getting on for an hour's outing, but only 20 minutes has actually been exercise.
It's vital that he gets out and about and sees as many new things as possible. Make sure he has several hours' rest between walks though!