Gatsby is only 10 months old. I run with them for maybe 100 yards max., and then its all stop because Daisy is on to a scent, and has to stop and figure out what it is. They can run very fast too; for short distances, in the 10-11 mph range. Even I could not keep that up for very long, but they will do it until its all STOP, and they stop on a dime, so running with my yorkies is not really all that fun!
I have thought about training them to only walk, but I figure we both benefit from the sprinting exercise. When I run, its more like 5-6 miles in the 8-9 mph range, so no, they do not go with me on a real run, they would never make it! In fact, I'm not sure how they would do on an endurance run vs a sprint, since they never make it too far before its all stop to sniff and pee. Another issue is when my girlfriend runs for a short distance too, when Ms Daisy gets too far in front she will at times circle back to be sure the pack is together.
