Many of us who "believe in" this problem are actually beginning to drop the use of the acronym and refer to these dogs more simply. I just say a dog has "early takeoffs" or a "vision issue" (if that has been proven to be the case).
I wanted to talk, briefly, about what is, and what should not be, considered an "early takeoff problem".
On occasion, Strafe leaves a stride out, somewhat inappropriately, and hits the peak of his jumping arc significantly before the jump. I would say, for that jump, that he "took off early".
Every dog will take off early on occasion. This can be caused by any number of factors, but primarily it is caused by dogs being dogs - an animal with a finite limit to its ability to adjust its stride while running. Ideally, our dogs would be able to adjust their strides AND the length of their jumping arc, but the peak of the arc should always be over the jump, whether they are extending or collecting. But of course, as I mentioned, mistakes happen.
Below, a centered, collected jumping arc.
However, a dog with generally normal takeoffs will generally takeoff normally. Some dogs are better judges of the appropriate place to take off than others - these are dogs we might call a "natural jumper" (regardless of training). They almost always arc appropriately over the bar, and probably don't knock many bars down either. They probably don't find spread jumps to be extra challenging either.
A dog with an early takeoff problem probably finds spread jumps to be extra challenging. This seems to feed into the hypothesis that the issue is probably vision-related (especially with regards to binocular vision or depth perception). There is some great research currently being conducted on dog vision using infant testing methods (so there is no feedback needed), but so far there is no consistent result for dogs with problems versus those without.
Along with spread jumps, tires are often very challenging for these dogs. This is a picture of my first border collie, who had a really bad early takeoff problem. I like this picture because it shows her looking fairly relaxed, and with not a bad jumping arc, although she's clearly coming down already even though she's just beginning to break the plane of the tire. Most of the issues noticed with early takeoff dogs is on horizontal lines, so it is interesting that the tire is something they struggle with. Most of these dogs have normal weave entries, even though the weave poles are skinny bars that should be just as hard to see as horizontal jump poles.
Sometimes, a picture is worth a thousand words. And if you suspect your dog may have a jumping issue, I would urge you to look at as many pictures of the dog as possible. One picture does not present an accurate picture of the dog's habits, just as one early takeoff does not either. But something I see a lot in dogs with early takeoffs is that, as in the picture above, it almost seems as if they don't know exactly where the bar is in relation to depth perception. Kiba looks like she's jumping "extra high", and she is, but it looks to me also as if she doesn't have a good grasp of exactly where the bar is. She has her front feet all tucked up, as if the bar is right there, but it isn't.
Now she's cleared it - she's also obviously on the landing part of her arc by now, and still isn't even close to "skimming" the bar. Interesting, for a dog whose primary fault is usually knocking bars!
Can you see the big difference here? Drifter has his head tucked down, his feet tucked up, but he's centering over the bar, and is going to clear it by just enough. He looks very confident about its location.
And he is confident. Not to say Drifter never hit bars, or Strafe either. (or Seri, who could jump with a hugely long jumping arc, but was usually centered over the bar)! But their mistakes usually come in the form of taking off too late. This, I do not believe is a mystery at all; it is usually an indication of a dog who got too caught up in what it was doing (jumping! yay!) and forgot to look "down the line" at the spacing, and so adjusted his stride too late and took off too close to the jump, causing a jump that looks a bit silly, where the peak of the arc is too late, and after the bar.
So the point I am trying to convey is; all dogs who do agility will make the occasional jumping mistake. Excited dogs may even make them fairly often. The difference for a dog with an early takeoff issue is that they make this same, strange mistake on most of their jumps; a majority of their jumping arcs are too early and they are almost always landing by the time they clear the bar. We don't know exactly what is causing this issue; many of us suspect it is either a vision, or visual-processing issue. Whatever it is, it seems to pass down in families of dogs. This would make sense, as vision is a heritable trait. It is certainly not going to be something as simple as coat color; even in humans vision heritability is still a bit mysterious.
Something else I want to emphasize is that, while some training may improve your dog's jumping, if he isn't sure where the bar is, you can't fix that. True early takeoff problems can be mildly improved with some training, but they won't magically disappear. So if you are a handler with such a dog, don't blame yourself! Another thing to note is that if your dog can't figure out where the bar is, and you correct him harshly for hitting it, YOU'RE NOT HELPING. Confidence should be the name of the game here. I've found adding some verbals for certain situations (especially for spread jumps!) has helped me tremendously with Kiba. Her issue is relatively mild, though.
Here is the video of my first BC, Freeze. She was incredibly intelligent and athletic, and tried very hard. I learned a lot from her about both jumping and about training a smart, sensitive dog. Please forgive the quality of the video - it is a video of a video playing on my laptop, but you should easily be able to see what I'm getting at. I had already been training dogs for agility for 7 years when I got this dog, we did jump grids, one jump work, tried jumping higher heights, jumping lower heights. All spreads, no spreads. We spent an entire winter once with tire set at 8" and a clicker and a bag of treats, just rewarding her for going near and through it (she was terrified of them due to a few horrible crashes). But in the end, I retired her from agility before she turned 7, and through some unusual circumstances not related at all to her agility career, ended up allowing her to live with a nice retired couple.
How anyone can believe this is a training problem is beyond me. How could I possibly train my dog to jump like this? Even if I tried, I could not formulate such a plan, because it isn't possible. It seems to be aggravated by the dog's confidence level being low, but a normal dog still doesn't respond by taking off too early on every jump (or nearly every one).