Teaching an old dog new tricks

Fat boy has been my trusted companion for eight years. Recently I decided we both lacked exercise and bought a leash and collar for him. The first walk started out almost nightmarish. I tugged on the leash, but Fat Boy wasn't in the mood. He sat on his hind legs and wouldn't budge. Eventually I did win out and we strolled with frequent sniff and territory marking intermissions, (Fat Boy, not me !!!) Things changed as soon as Fat Boy realized we were on the return trip. He ran like hell, me trotting behind.  I got more exercise than what I'd planned. Maybe I should consider roller blades