Chopper is presenting to his fellow canines the fine-tuned way of walking on a treadmill. Dogs learn a lot from each other just by observation and mimicking that's why it's so important to show them what we DO want for them to do so they have a good role model (you, the pack leader) to follow. 

One of the fine-tuning and mentally stimulating exercises that teaches dogs self-control, patience, focus, respect towards the pack leader and that fulfills their instinctual need to "hunt" for food is our "Super Bowl" game. The calmest and the best mannered dog gets to eat first. In this movie, all dogs did great so they could enjoy eating together as a pack. :)