@liza84 I have great respect for Dr. Millis.
But this article doesn't really provide much useful info beyond the general guidelines at the end. No one is saying that normal puppy run-around, wrestling, free play, exploratory walks, etc are harmful to a puppy. So that seems like a silly point for Dr. Millis to bring up.
As far as the section on regular exercise - I had read the (horrendous) Beagle studies when this article was posted elsewhere. The studies were small (n= 6-10), there's no info on whether the dogs were intact or early neuters, in one study the exercise was very gradually increased from 15-25 weeks of age before ramping up, there's no long-term assessment of degenerative joint disease, since they were euthanized young.
This article also mentions a study where dogs walked for 75 mins per day at a speed of 3km/hr (1.9 mph), 5 days per week. I cannot access that study in any database that I have free access to. But how old were these dogs? A mile in about 30 minutes is a very slow walk. I don't think anyone believes that walking a healthy adolescent or adult dog five days a week at a slow speed for less than 2.5 miles is going to cause joint issues.
One big issue for me is that the vast majority of dog owners don't know whether their dog already has a predisposition to dysplasia or OCD or other joint disease when they are puppies. So they have no way to know whether moderate forced exercise (like excessive structured walking with owners, or forced running with owners) might lead to further degenerative issues. I believe that there is some research that indicates that cartilage that is already "under assault" from lowered amounts of GAGs (like glucosamine and chondroitin) is more likely to suffer further damage from too much weight-bearing exercise.
Last, the whole idea that pediatricians don't worry about kids getting too much exercise is because no parent in their right mind would force a toddler to run for a half mile, or force an elementary school child to run for five miles. Toddlers know when to stop running around (when their bodies signal to do that), and would just throw a huge tantrum on the ground if forced to go further. But many active energetic puppies running on leash with owners will try their best to keep up past the point where they would have stopped if playing in a normal environment with other puppies. Puppies run around, take breaks, run around again, take a nap. They don't run for miles straight.
(And pediatricians and pediatric physical therapists
will tell you that children who play one sport to excess can develop joint and soft tissue damage. There are studies that point toward increased bowleggedness and other changes to leg joints in children who play on high level soccer teams. And there's a reason that young baseball pitchers are restricted in the number of pitches they are allowed to throw per game and per week at a given age.)
So that's my non-veterinarian take on the issue. I guess that makes me one who errs on the side of caution in terms of repetitive stress or impact stress until a puppy is well on the way to adult size.
TL;DR: better safe than sorry, and the puppy can still have a totally fun and happy time even with some restrictions in place.
