Cantering on a horse is probably one of the most enjoyable things we can do in riding. Faster than a trot, but not as fast as a gallop, it is ground covering and has an almost mesmerizing rocking motion. It is surprising how many people don't know the way a horse canters.
As an instructor, it is obviously important that I know such things, and I believe I do. Besides taking lessons for many years, I have also read volumes and observed horses cantering on the lunge and being ridden. Not to mention schooling horses under saddle.
First, to separate canter from the other gaits, I will explain the gaits. The walk is four beats, the trot is two beats and works on diagonal pairs. The trot pace, is a unique unnatural gait that works on leg pairs of the same side. The canter is three beats and the gallop is four. So, what is the difference between canter and gallop? They are almost the same. Obviously the gallop is faster than a canter. It is the fastest gait. But the technical difference is that, well, I'll describe canter first.
The canter haas three beats. It is asymmetrical, unlike walk or trot. The first footfall of the canter depends on which direction you are going. So for example if you are going to the right, you would be said to be on the "right lead". The horse would be bent right and turning right. But here is where most people get confused. The leg that begins the right lead canter and strikes off, is the left hind. That is the first beat. The second beat is the right hind and left front together, just like a trot diagonal. Then the final third beat is the right front. After the right front touches down, the horse is airborne briefly. This is known as "the moment of suspension" After this suspension, the sequence repeats. (See Slideshow)
So what makes the gallop different? Because of the speed the second beat where two legs would land together like a trot diagonal split. So for a right lead gallop the sequence would be left hind, right hind, left fore and then the right leading leg.
Because the horse must begin, or strike off with his outside hind to canter in the desired direction, the aid for the rider is their outside leg, either a nudge, pressure or a kick. Usually the outside leg is brought back a little or more depending on the horse's training and rider's skill. If you are riding a turn or circle, the outside leg should be a little back anyway. These are nuances for skilled riders. For a green horse or rider sometimes a good kick with the outside leg back is needed. It all depends on horse and rider. Horses can also learn a voice cue. The inside leg of the rider remains active at the girth to keep the horse forward.
Horses make mistakes in canter. Sometimes they get a wrong lead, even if asked correctly. They can also canter correctly with hind legs, but have the front legs going the opposite way! This is called cross cantering or disunited canter. I have also seen horses canter with one pair of legs and trot with the other. All of these problems are due to the horse's imbalance. This is where dressage traiing helps to balance the horse. An injury could cause a horse to favor a certain lead, or not obtain the correct one at all. Usually when riding, the rider can tell that one lead is easier tha the other - again, depends on the horse's degree of training and balance.
Changing leads is another challenge to the horse and rider, but can be fun. The easiest way to change a lead is to just bring the horse back to trot or walk and then give the correct cue for the new lead. This can even be done from a halt! i.e. canter left, halt, canter right. These are called "simple" changes. More difficult is to change the lead without changing gait. The horse makes the switch, on cue, during the moment of suspension. This is called a "flying" change. Horses can, and often do this naturally of their own will when at liberty, but is harder to get correct on cue when ridden. To switch leads after so many strides ie. two strides, four strides, or even every stride are called "tempi" changes. This is mostly seen in higher level dressage tests. What fun, and so beautiful to watch, like dancing!
So there you have it from the most basic to the most sublime. Who doesn't love to canter?