Trotters and Pacers

Since Cecil brought up human beings, it’s worth noting that we hominids are trotters by nature.

Seriously, try crawling (or watch a baby crawling), and you’ll find that we naturally move our left arms and right legs together, then our right arms and left legs together.

Standardbred horses are classified as either trotters or pacers. There are usually more pacers than trotters, since the gait is easier to train and (more importantly when betting is concerned) they are less likely to get off gait*. There are devices called “hopples” for pacers – tying the horses right side or left side leg together so they stay in unison – but that doesn’t work for trotters since the two hopples would cross and trip the horse.

*If the horse stops trotting or pacing, it has to be pulled up out of the race until it’s back on gait again. This costs time and usually means the horse finishes out of the money. Bettors don’t like that at all.

That’s walking, not trotting. And it’s actually moving your left arm, then right leg, then right arm, then left leg. Almost all quadrupeds do that, even the dogs that are referenced in the original column. Pacing and trotting involve two limbs in the air simultaneously. (And galloping gets all four legs off the ground, for the record.)
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That might be true for the USA but not for the rest of the World, at least not in Europe.

Well, when I crawl, I get two limbs off the ground simultaneously. Admittedly my knees don’t like it, so I ease into them a little, and my hands make contact first, but I do have two limbs off the ground at once.

Well, yes, but there’s still a distinct difference between the walking gait and the trotting gait. It’s hard to describe in words. While you do sometimes have two limbs off the ground in a (4-legged) walk, one is coming down while the other is going up, and you end up with three limbs on the ground during most points of the gait. In a trot (or a pace), the limbs move in pairs, simultaneously.

Google around for some pictures (videos don’t really show it well unless they’re slo-mo).
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The differences between walking and trotting are due to bipedalism versus quadrapedalism and the significant differences between our legs and arms. A crawling babies walk on their knees and can either use hands or forearms but almost never their elbows. In contrast, walking humans tend to move the right arm in concert with the left leg, and the left arm with the right leg. We crawl differently than quadrapeds trot, but even so, the most natural crawling pace involves a right, left right left motion and not right right left left. Even given the difficulties we have in this area (try to imagine on your hands and toes instead of your hands and knees), it’s easy to see why babies move to a bipedal stance shortly after learning to crawl but I bet at babies that are crawling fast, the motion will come pretty close to a trot. Likewise, chimps and gorillas knuckle walking move opposite limits in concert, even if the motion is not

Nonsense. Quadrupeds walk all the time.

Look at a dog walk, and then look at him trot. The order of leg movement may be the similar, but the duration of contact with the ground is very different. Furthermore, and even more importantly, walking is a 4-beat gait (for quadrupeds), meaning no two legs move in unison; trotting (like pacing) is a 2-beat gait (first one pair of legs, then the other pair).

Of course, looking in real time is hard, so photos and slow-motion video will tell the real story. Here’s a site with some good animations: http://emg-zine.com/item.php?id=779
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