If you’re around the horse world long enough, you’re bound to hear people talking about breakover. What, you may ask, is breakover? Well, there are two definitions. The first, as defined by Dr. Hilary Clayton in The Dynamic Horse, is –
Terminal part of stance phase during which the heels of the hoof rotate around the toe, which is still in contact with the ground
In other words, breakover, or breakover time, is the amount of time it takes for the hoof to actually leave the ground after the heels have lost contact with the ground. The second definition, also referred to as the breakover point, is the physical location of that rotation “point” on the bottom of the hoof.
Some horse people get quite caught up in trying to hasten breakover (time) by attempting to move the breakover point farther back towards the horse’s heels. In fact, there are many, many shoe designs that purport to do exactly that – hasten breakover by shoes with modified toes. And yet, according to the notes of Dr. Clayton’s presentation at the Wild West Veterinary Conference in October 1997 entitled Farriery Manipulations – What Works? –
For horses trotting on a hard surface, the duration of breakover was no different for a rolled toe, a rocker toe or a square toe compared with a flat shoe (Clayton et al., 1991). Willemen et al. (1996) also evaluated the effect of rocker toed shoes in sound horses and failed to find changes in breakover, the flight arc of the hoof or tension in the DDFT (deep-digital flexor tendon) at breakover…
Therefore, based on the data (which, I might point out, has been around for 20 years), it would seem these shoe modifications fail to live up to their claims. Yet this persists as a very common misconception about a commonly-used type of shoe. The only thing Dr. Clayton found that improved breakover, according to personal communications with me in the mid 1990s, was keeping the hoof as short as possible. Sounds like yet another “plus” for barefoot to me!
And while I did want to share that general information with you, I mostly want to talk about another consequence of using shoes with modified toes. While at the White Stallion Ranch at the end of last month, I decided to take a look at the wear pattern on some of the horseshoes that had been removed and tossed aside. Although, strictly speaking, I didn’t utilize a proper sampling plan, I searched through several dozen shoes and pulled out all of the ones exhibiting any wear at the toes, regardless of the wear pattern itself. So the sample is representative of wear patterns, but not representative of all used shoes.
Why did I want to mess with at a bunch of old, rusty shoes? Because I’ve noticed before that shoe wear tells a very important, yet apparently ignored, fact about equine movement. So, having now explained breakover, let’s take a look at these two photographs of worn shoes –
Notice anything interesting? Here’s what I see: of the 31 shoes collected, at least 22 of them (71%) clearly demonstrate that breakover does not happen squarely over the toe! As you can see, in more cases than not, the wear isn’t symmetrical about the toe of the shoe.
What happens when a horse that doesn’t break over squarely at the toe wears a shoe that attempts to force him to break over at the toe? Stress, that’s what! With every step, the limb attempts to carry the hoof off the ground in one direction while the shoe tries to force it in another. And that translates to unnecessary strain on the coffin, pastern, and fetlock joints, especially as the speed of the horse increases, because those joints just aren’t designed to articulate in that manner.
So the lesson is this: if you genuinely want the best possible movement from your horse – the fastest breakover, the least stress, and the most shock absorption (more on that one later), keep the hoof bare and properly trimmed. Ignore those who try to convince you otherwise, and point them to the data. It’s every horse’s best chance at long-term soundness.