Maybe Tom might know something about this. I was wondering if anyone has slow motion studies of this. ?
Yes, actually we do have some slo-mo of Posh. I use my "golf swing" camera for it, but I haven't gotten the right combination of lighting and shutter speed yet to get a clear video like I want. It's just been too hot to do anything outside with it lately. The cameras a fairly inexpensive Casio that will do up to 1,000 fps, but quality suffers as the frames per second go up. 240 is not bad in full sunlight and with ideal conditions and plenty of light it does pretty good at 400 fps. I'm avoiding full sunlight every chance I get now though. It was 103 here today. I'll definately have some this fall though. We're planning to add a page to our website on conformation and movement.
The quoted description in the first post is in the new standard that was voted on not too long ago by the parent club. It's been a while since I compared it to the last standard, so I don't really remember if it was carried over or not. I haven't even kept up with if AKC has approved the latest version yet, so it might even be the last version.
There is actually a LOT of variation in gait with dogs within the breed. Dogs that flip their front feet up to show "flash of pad", typically don't have great drive from the rear end, so the flip up of the toes is really sort lost, or extra, motion. Some breeders say that they breed for it, and it does well in the Toy ring, but we have always looked for strong rears from our experience in breeding Sporthorses (horses that do the Olympic events). We don't want limited movement in the back so we can have front feet flipping up. If you notice Posh's movement, the pads of his front feet don't flip up much, but are reaching for their next strike down point. Posh's movement is what we want to reproduce, and have been for a while now.
You might notice Twinkle's movement in her 14th Birthday video. Most people look at the front conformation with complete disregard for the rear conformation. Twinkle actually has a fairly straight shoulder with maybe 28 degrees of layback, but she has a great back end with a stong loin, and long femurs, so she drives that front end just fine, even at 14 years old.
There is great variation in rear assemblies. Some call for "short hocks", which is indeed a good thing, but not only for the sake of just having low hocks. Low hocks (less than 1/3 of rear height) are biomechanically more efficient, but allow for more of the rear leg to be in other parts. A dog can have low hocks, and a short femur, because it has a disproportionately long "gaskin" (gaskin is a horse term for the part of the rear leg between the stifle and the hock. The stifle is the joint between the femur and the tibia and fibia, and the hock is the joint between the tibia and fibia (gaskin for short). A lot of dog people talk of the hock as being the whole part of the rear leg from the hock down. To keep this simple, I'm just going to call that part of the rear leg between the stifle and the hock, the gaskin for dogs too.
In Sporthorses, we want the stifle to be below the elbow. This is the same thing that we are looking for personally in our dogs' conformation too. It does make a difference.
The largest muscle is the quadricep, just like ours are out largest muscle. It's attached to the femur. Femur lengths vary greatly in this breed. A longer femur can have larger quadriceps. A larger quadricep on a longer femur is more powerful when reaching under. It can support more of the dogs weight while the rear foot is all the way forward, and add more bounce to the step by propelling the body weight up as well as forward. "Spring" comes directly from what the back leg is able to do.
So the largest importance of having short hocks, is that it maybe allows for a longer femur. A longer gaskin gives a weaker rear leg, and dogs whose rear legs wobble back and forth when trotting usually have a short femur and long gaskin, which can be in spite of having low hocks. There can be any combination or lengths between the various parts of the rear leg. There are MANY possibilities of combinations, and if one bothers to look, you will see great variation.
Long story short, there's lots of variation in locomotion in Havanese. When Standards change it's usually from persuasion by some influential breeder, and also what's doing well in the show ring, which is dependent on the amount of money spent as much or more so than a particular type being "better".
Personally, we have always, and will always go for efficiency of movement. Not only do we like it best, but it holds up well over time.
I used to do consulting on Sporthorse breeding and teach conformation, but it got to the point that newer people didn't really want to learn, but rather just be told who to breed to, so I got tired of doing it.