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Locomotion

Last revised April 15, 2017.

Locomotion is most typically expressed as walking from one place to another, as seen in this feral horse stallion. The higher energy-expense gaits of trotting, cantering, and galloping are observed far less frequently.1

The moving horse is incredible. It evolved for speed and endurance, and thousands of years of selective breeding further improved his speed and stamina. The horse has one of the highest running speeds (70 km/h or 43 mph) of mammals, and is easily the fastest animal to be able to carry a human.2 The great claims for the speed of the cheetah (over 70 mph) must be considered in light of the short distance it can maintain such speed: the cheetah can’t maintain its top speed for more than a quarter of a mile, and has been brought to bay by two dogs in 2.5 miles. The horse, on the other hand, can maintain a speed of about 15 mph for a distance of 50 miles.3 Researchers find that the horse’s maximum aerobic power output is 3.5 times higher than the value predicted by general formulas for mammals.4

Gait

Gait refers to a cycle of limb actions that an animal uses repeatedly when moving. In humans, we have the walk (feet alternately touch the ground, with one lifting only after the other has come down), run (feet alternately touch the ground, with one lifting before the other has come down)5, hop (one leg only), skip (one leg strikes ground twice, followed by the other), and jump (both legs push off, and the body is briefly airborne.) To move from a slow walk to a fast walk, the human increases both stride length and rate. Cheaters would say that’s five gaits, but like horses, most of us make do with just one.

Different breeds of horse may differ in the gaits they have available, and a horse can be taught a gait that is not normally in his breed’s repertoire. Most of the many possible gaits derive from walk (and amble), trot, pace (rack), canter, and gallop. Gaits differ in their average speed and the sequence in which feet leave or strike the ground.

Several classifications are used to sort gaits. Asymmetrical gaits are those where the left and right side are not mirror images. These differing actions on left and right are found in the canter and gallop.

In an asymmetrical gait, the animal favors one of his two rear legs for drive. A horse has a right or left lead based on which side he is predisposed to turn toward. At a canter or gallop, the horse can control the lead they are using, switching as circumstances or fatigue dictate.

Basic gaits

About the diagrams:

  • For each gait, I use the code LH (left hind), LF (left fore), RH (right hind), and RF (right fore). All gaits come in a cyclic sequence, and it doesn’t matter where we start.
  • A black block means the foot was on the ground, supporting weight. At a walk, the heel is the first to leave the ground, the toe is first to return to the ground — though the landing is very close to being flat footed.
  • With only 12 frames per stride, some details are lost and must be inferred. For example, is the foot starting to lift between frames 10 and 11? I have “rounded” my patterns below, to show a horse evenly performing each gait (eg., each foot is in the air for 4 frames, then down for 5.)
  • When constructing these diagrams, I show a white space whenever the foot is fully in the air, as well as when only the toe is touching the ground, as it is not supporting weight at this time. The sequence of feet landing and sequence of taking off can be inferred, as can be the ground contact time and time in the air. You will see that at faster strides, the feet spend more time in the air, but the time for each foot on the ground does not change much.
  • All patterns were determined by studying photos in “Muybridge’s Complete Human and Animal Locomotion” by Eadweard Muybridge.6 Muybridge took still photos at rapid fixed intervals, depicting a stride in 12 or 24 frames. Where possible, I have used photos with 24-frame sequences where the legs can be clearly distinguished in all photos. But some of his clearest plates are only of 12 frames per sequence, so when I could not be certain about 24 frames, I used 12 frame plates.

Walk. 4 beats. Each leg shows independent movement. About 4 mph (range 2-5 mph). Sequence is left hind, left fore, right hind, right fore. Beat is a regular 1-2-3-4: each hoof moves forward at an even pace, with an even interval between each footstep. At the walk, the horse will alternate between having two or three feet on the ground.  The horse will bob his head slightly for balance. Rear feet may overstep the spot where the front foot on that side touched down. The greater the overstep, the more comfortable the walk becomes for the rider. Horse motion for a rider is a gentle side-to-side sway. About 40% of the horse’s weight will be loaded on the back legs when walking.

The sequence:7

4 2
3 1

Amble. 4 beats. Any of several gaits between a walk and a canter. Ambling gaits include the Fox trot, the Lateral slow gait (stepping pace) the Paso gaits (Paso fino, paso corto, paso largo), the Rack, and the Tölt. According to Wikipedia, Some ambling gaits are lateral gaits, meaning that the feet on the same side of the horse move forward, but one after the other, usually in a footfall pattern of right rear, right front, left rear, left front. Others are diagonal, meaning that the feet on opposite sides of the horse move forward in sequence, usually right rear, left front, left rear, right front. A common trait of the ambling gaits is that usually only one foot is completely off the ground at any one time. Ambling gaits are further distinguished by the timing and cadence of the footfall pattern. One distinction is whether the footfall rhythm is isochronous, four equal beats in a 1-2-3-4 rhythm; or a non-isochronous 1-2, 3-4 rhythm created by a slight pause between the groundstrike of the forefoot of one side to the rear of the other.8

A sequence9 (many other sequences possible. In the pattern below, the horse keeps his left foreleg in the air a bit longer than the others):

Pace. 2 beats. Two legs from one side leave the ground, and when they come down, the two on the other side lift. The effect is a gentle rocking from side to side. As speed in the pace increases, the rocking becomes more rapid. Camels pace, and at speed are more comfortable than a fast pace on a horse, because camels have a longer stride length. The ability to pace may be inherited.

The sequence:10

Trot. 2 beats. Diagonal legs move at the same time. Sequence is right hind and left fore, then left hind and right fore. Twice in each complete stride, all four legs are off the ground. The horse finds this gait very stable, and can trot for hours. In a “sitting trot”, a rider will find that the horse bounces up twice per complete stride, sending the rider up out of the saddle. As gravity returns the rider to the saddle, it is rising again. Posting solves the problem for horse and rider: rising from the saddle on every other beat, and returning on alternate beats. When a horse needs to travel quickly, the trot seems to be his favorite gait. About 8 mph (range 7-10 mph). A jog is a slow version of the trot. About 50% of the horse’s weight will be loaded on the back legs during a trot.

The sequence:11

4 2
3 1

Canter. 3 beats. A sequence in which one fore leg is followed by the other fore as well as the diagonally opposite hind, and then the remaining hind. For a left lead, the horse drives with his left rear leg, and the remaining feet are briefly in the air. The three beats occur in close succession, followed by some quiet air time. Cantering is tiring for the horse, who must support his weight with two legs (a foreleg and diagonally opposite hind), but cantering is easier on the rider than when at a trot. 10-17 mph. A lope is a slow, relaxed canter performed with a loose rein, and most often seen in western (U.S.) horses. A canterlope is a melon. About 60% of the horse’s weight will be loaded on the back legs during a canter.

The sequence for a right lead:12

Left Lead 3
2 2
1
Right Lead 2
3 1
2

Gallop. 4 beats. Rear legs drive, front legs try to keep up. The footfall pattern of the gallop on the left lead is right hind, left hind, right front, left front. Likewise, the right lead footfall would be left hind, right hind, left front, right front. Feet land in rapid succession, and then the horse is airborne for the remainder of the stride. Legs are together when airborne; when legs are stretched out, one rear foot will be on the ground. Range 25-30 mph; top speed perhaps 40 mph. About 30-50% of the horse’s weight will be loaded on the back legs during a gallop.

The sequence for the left lead:13

Left Lead
4 3
2 1
Right Lead
3 4
1 2

Back. 2 beat diagonal gait. The pattern of footfall looks like a trot in reverse. About 70% of the horse’s weight will be loaded on the back legs.

2 1
1 2

Special gaits

(in alphabetical order):

  • Flying pace (pace). 2 beats. A lateral gait — legs on one side drive while legs on the other side are off the ground, then legs on the other side drive. (In the trot, it is diagonal legs that operate in unison.) After one side has driven the horse is briefly off the ground, before coming down on the other side. Found in Icelandic horses that have two copies of the mutant DMRT3 gene14, and the gait of Standardbred harness racing horses.15 Very fast — about 30 mph — the speed of a full gallop.
1 2
1 2
  • Fox trot. 4 beats. The only diagonal ambling gait. Diagonal footfalls occur in couplets of 1-2, 3-4. Lots of head and neck bobbing absorbs the shock, and the rider experiences no vertical movement. Can be performed by Missouri Fox Trotters and some Tennessee Walking Horses. A variation on the Amble (see above).
2 1
1 2
  • Lateral slow gait (stepping pace or amble). 4 beats. A slightly uneven lateral slow gait, with a non-isochronous 1-2, 3-4 sequence. The stepping pace is faster than a running walk and extremely smooth, but not as energy-efficient. It is a smooth gait at slower speeds, but at faster speeds can turn into a 2-beat pace. Can be performed by some Tennessee Walking Horses. A variation, called the sobreandando, is found in the Peruvian Paso. A variation on the Amble (see above).
2 4
1 3
  • Paso fino, paso corto, paso largo. 4 beats, with an even 1-2-3-4 rhythm. Paso fino is the slowest, paso corto is like the moderate speed of the rack or singlefoot, and the paso largo is the fastest form of this gait. Each variation is accomplished by a change in stride length. Performed by Peruvian Paso and Paso Fino breeds. A variation on the Amble (see above).
  • Passage. Trotting in place, with a little more forward motion than the piaffe. Not particularly functional, advanced dressage horses can learn it.
4 2
3 1
  • Piaffe. Trotting in place, with a high slow step and little forward motion. Not particularly functional, advanced dressage horses can learn it.
4 2
3 1
  • Rack (singlefoot or single-foot). 4 beats. An amble, in which the gaited horse rocks side to side with an isochronous, even 1-2-3-4 rhythm. Only one foot is off the ground at a time, making this gait much more comfortable for a rider than the trot. Can be performed by Racking Horses, American Saddlebreds, some Tennessee Walking Horses, and some horses within many other breeds. Racking is often the result of soring (see below). In speed racking, there is a minimum of one foot on the ground. Speed racking is very fast, very smooth, and must be exhausting for Mr. Horse, though many claim that a Racking horse can rack as easily as other horses trot or canter. A variation on the Amble (see above).
  • Running walk. 4 beats. Same footfall pattern as a walk or flat walk, but significantly faster. In the running walk, the horse’s rear feet overstep the prints of its front feet by 6 to 18 inches (15 to 46 cm). The horse’s head and neck bob — even more than in the Fox Trot — during this gate, helping him keep his balance. Speeds 10 to 20 miles per hour. Most often performed by Tennessee Walking Horses. A variation is the paso llano, performed by the Peruvian Paso.
4 2
3 1
  • Stepping Pace (pace or slow gait). 4 beats. A slow lateral gait with a broken pace: two legs on one side leave the ground together, but land at slightly different times. The rider experiences some bounce, but far less than at a trot. Performed by the five-gaited Saddlebred, Tennessee Walking Horse.
  • Tölt (or tolt). 4 beats. A very, very smooth, rapid lateral ambling gait, found mainly in Icelandic horses. Very similar to the rack. Footfall corresponds to that of a walk. Unique to the Icelandic horse and its descendants: the Faroese and the Nordlandshest/Lyngshest horses from Norway. Horses with a strong natural ability to tölt are likely heterozygous for the DMRT3 mutation (see below). Can be performed at the speed of a fast walk up to the speed of a canter. A variation on the Amble (see above).
4 2
3 1

We need some serious work defining these gaits, and studying them in slow motion, because after compiling the lists above, I’m still left with a number of gaits that may exist, may be more common gaits with odd names, or may not exist. Consider the Flat walk. 4 beats. A walking lateral gait. Missouri Fox Trotters can do this.

The canter and gallop are regarded as asymmetrical gaits because right and left limbs have different actions (the actions are not mirror images). Asymmetric gaits favor turning toward one side or the other, and a horse is said to be in a “right/left lead” according to which side it is predisposed to turn toward, at the canter or gallop. Horses control which lead they are using, and change leads to reduce fatigue.

Ambling gaits (ambles) are those four beat gaits that are faster than a walk and usually slower than a canter. In the U.S., horses that can amble are referred to as gaited. From the standpoint of the fit horse, a gait may be maintained for long distances. From the standpoint of the rider, the amble is wonderful because it is so smooth, and thus ideal for all kinds of riding, particularly for long distances.

Nature and nurture both contribute to a horse’s range of available gaits. From breeding, a horse may get gaits that don’t come naturally to other breeds. From training, it is likely that any gait can be taught to a horse that does not naturally possess it.

When a horse moves on its own, it likely chooses the speed it wishes to go, and from that selects a gait that provides that speed with the least exertion.

Both horses and their predators can move fast. A horse’s legs are specialized for locomotion. Because their diet is roughage, they must have a bulky digestive system, which requires a somewhat rigid trunk. Speed is helped by long legs, and joints that keep legs in the plane of movement. A horse’s predators are also fast. Their legs are not as well designed for running as a horse’s, because they must also be able to manipulate, climb, and do other things with their legs. But because their diets include meat, their digestive systems are not so elaborate, and their trunk can be more flexible. A lion gets a long stride length because it can flex its spine.

Within a trot or withing a gallop, there is a great range of speed possible. For a variety of animals ranging from mouse to horse, top speed at a trot is about 2.6 times as fast as minimum speed at a trot. And top speed at a gallop is 2.1 times as fast as minimum speed at a gallop.

Gaits are fairly easy to identify, but not very easy to describe. To the rescue comes Eadweard Muybridge (born “Edward James Muggeridge”, but he changed his name four times), who has been called the “Father of Cinema”. Muybridge photographed and published “Animals in Motion”16 and “The Human Figure in Motion”17 “Animals in Motion” contains 3,919 photographs of 34 different animals and includes Edweard’s observations on the movements. “The Human Figure in Motion” contains 4,789 photographs of humans engaging in various activities. Both books can still be bought today (on Amazon, for instance) and are widely studied by art and animation students. His motion photography exploited fast shutters and sensitive film. It also used multiple cameras. To capture 12 frames, he set up 12 cameras with 12 trip wires, then had a horse run through them. All 12 photos were taken in less than half a second. His results astounded the world, and astound us still today. I’ve provided his photos of a horse walking, trotting and galloping below.

A horse walking. Photogravure made by Eadweard Muybridge, 1887.18

 

A horse trotting. Photogravure made by Eadweard Muybridge, 1887.19

A horse galloping. Photogravure made by Eadweard Muybridge, 1887.20

Gait Keeper Gene

Studies of the DNA of naturally gaited horses have found that a small mutation on a single gene (DMRT3) is the source of gaiting.21 Icelandic horses that have five gaits (walk, tölt, trot, gallop and pace) are normally homozygous for this mutant gene, whereas only 31% of Icelandic horses with four gaits (walk, tölt, trot and gallop) were homozygous. The mutant gene is critical for both diagonal and lateral ambling gaiting.

This gene controls the spinal neurological circuits that control limb movement and motion. The mutant gene permits alternate gaits, including a fast trot used in harness racing horses. It facilitates lateral gaits, ambling and pace, and it inhibits the transition from trot or pace to gallop. It seems to deny the ability to gallop in some horses but not others22 — not a hardship to owners of these wonder horses.

This mutation is only known to have occurred once, in what is now England, in 850 to 900 AD.23 Vikings visited the village where this horse lived and took some of them home. The Vikings first settled Iceland with their livestock around 870.24 It is said that no other horse has entered Iceland since, so Icelandic horses are very pure, very much like the originals brought by the Vikings.

It is believed that all gaited horses are descended from this one gaited horse in England. This mutated gene has been identified in the Missouri fox trotter, the Paso fino, the Rocky mountain horse, the Icelandic horse, the Tennessee Walking Horse, the Peruvian Paso, the Standardbred trotter, Standardbred pacer, the Kentucky Mountain Saddle Horse and any other horse born with five gaits. Some individuals from these breeds may be heterozygous for the special gene, in which case they would only have a 70% chance of showing a special gait. The gene may be tested for.25

Biomechanics

A horse is built to move forward, and finds backing up quite difficult.

A horse’s center of gravity is normally just behind the withers. He can shift it forward by lowering his head and neck, and shift it back by raising his head. Moving his head to the side will shift his center of gravity to that side.

A horse initiates forward movement by pushing off with one back leg. This moves the center of gravity forward and towards the front leg on the opposite side. That leg then moves to support the new center of gravity. When a horse is walking, the center of gravity shifts from side to side, and his body swings from side to side. At faster gaits, forward momentum increases, and lateral oscillation is reduced. As a result, hooves hit the ground closer to the medial plane. With more forward momentum, fewer feet need to be in contact with the ground at any moment. At a gallop, there is a phase when no foot is on the ground.

At one phase in the gallop, no foot is on the ground.26

Propulsion. Most of the propulsion in a horse comes from the back legs, which move the center of gravity forward and upward as they push off. The back legs are heavily muscled, and connect directly to the spine. The back legs provide the power to move forward.

The front legs are shorter and straighter than the back, less heavily muscled, and don’t connect to the spine with a joint. Rather, the forelegs connect to the scapula, which attaches to the body with muscles, ligaments and tendons. Unlike humans, there is no clavicle. The job of the front legs is to catch the horse as the front end comes down, and provide directional stability. If pulling a cart, the front legs contribute directly to forward propulsion.

The neck has a very important role in locomotion. In all gaits of the dog, the neck flexes with each step of the forelegs. The horse’s heavy head and long, heavy neck is important to the horse in control and balance during locomotion.27 Restraining this motion with a martingale might leave you feeling like you are in better control, but it will reduce his control and balance.

Conserving energy. It has long been known that humans break into a run from a walk when the desired speed is more metabolically expensive at a walk.28 More recently we have learned that horses choose between walking, trotting, and galloping gaits to minimize the energy they consume at any given speed.29 When it comes to changing gears, animals have an automatic transmission.

Light weight design. During the horse’s evolution, natural selection favored long and light in the horse’s frame. While a horse may not feel very light when he is standing on your foot, in fact, his legs are proportionately much lighter than ours. This lightness has come about in part because the main bones became thinner as they became longer, and because many bones were simply discarded.

If we compare our own anatomy with that of the horse, we see that our scapula, ankle, and wrist are stretched in the horse. The ulna of the forearm and fibula of the leg have become vestigial spurs in the horse, and the clavicle has disappeared, along with all but the middle finger and toe.

Comparative view of the skeletons of a man and a horse.30 A is for ankle and W is for wrist, both much stretched in the horse, and all but the middle finger and toe have disappeared. K is for knee and E is for elbow, both raised up into the horse’s trunk. S is for sternum. The horse lacks the human’s clavicle. The ulna of the forearm and fibula of the leg have become vestigial spurs in the horse.

The evolution of the horse sacrificed some skeletal strength for speed. They dealt with impacts by changes that limited the lateral movement of their limbs and by matching the posture of limbs with the forces of impact when moving. Under normal conditions, there is enough of both for the horse to make do just fine. But pushing a horse hard frequently can stress or break bones.

Respiration. When a turtle or lizard runs, they have trouble breathing.31 When a human runs, our rate of breathing and stride rate don’t match, sometimes being 1:1 but ranging up to 1:4. But other fast-moving mammals such as hares, dogs, bats, gerbils, rhinoceroses, wallabies and horses32 may synchronize their breathing and stride, taking exactly one breath per stride when moving faster than a walk. Birds appear to take a breath with each wing beat. Phase-locked locomotor and respiratory cycles evolved independently in birds and mammals, but both must have discovered a benefit of it. In both birds and mammals, the muscles powering movement also play a role in regulating air flow, and the synchrony adds to the animal’s efficiency in sustained aerobic exercise.33

Several theories have been advanced for how birds and many mammals do this.

  • Some have speculated that when the front legs hit the ground, the chest is squeezed, forcing air out of the lungs. There is little support for this idea in research done since the idea was proposed.
  • Some have speculated that when the front legs reach forward, the organs are pushed up against the diaphragm, forcing air out of the lungs. This does seem to be the case with dogs: when a dog trots, it appears that the stride rhythmically jostles the viscera, coordinating respiration.34 And it seems to be the case with wallabies, who seem to have a “visceral piston mechanism tuned to stride frequency.35
  • What’s true for dogs and wallabies doesn’t seem to apply to horses. Researchers36 who studied film synchronized with respiratory flow measures for horses on treadmills concluded that neither theory could fully account for breathing. Their suspect: back flexion drives breathing. Galloping quadrupeds flex and extend the lumbar region of the back with every stride,37 and so this flexion would provide a handy respiratory pump.

Subsequent research also points to the horse’s flexing back as the source of synchrony between stride and respiration.38 This does not seem to be resolved yet, but I believe that both the oscillation of organs (especially the liver, which is attached to the diaphragm) and the oscillation of the spine provide the incentive to breathe in coordination with stride.

Flexing of the spine or adequate oscillation of the organs may not occur at a walk or very slow trot or when pacing, explaining why this synchrony doesn’t occur at those speeds.39

Average ground contact pattern of the four limbs (filled horizontal bars) in two horses is shown during locomotion at different velocities as a function of the fractional duration of the locomotor cycle. The horse is on a horizontal treadmill on the left of the figure (A), and an inclined treadmill on the right (B). The open vertical bars represent the percentage frequency distribution of the onset of inspiration during the corresponding locomotor period (scale range, 0-100%). LF, left forelimb; RH, right hindlimb; RF, right forelimb; LH, left hindlimb.40 Respiration begins to synchronize with stride at a trot and becomes entrained as speed or load increases.

Studies of horses show that stride and breathing are not synchronized at every gait.41 They appear to be synchronized at a canter and at a gallop, and at a fast trot. I’m guessing that any strides that are more effortful than a fast trot will show this synchrony.

If a horse draws exactly one breath with each full stride, how does a horse handle a steep hill, where oxygen demands will be greater than on the level? Turns out that the horse simply breathes more deeply, increasing his tidal volume.42

Velocity and stress. When a horse is moving forward at a steady speed, his hooves impact the ground at his speed of travel, so the only trauma comes from the compression caused by his weight. In this respect, a gallop over a level surface is no harder on the horse than a walk. But when a horse accelerates or decelerates, the hoof impacts the ground at a different speed than the horse is traveling, adding trauma to the leg. During acceleration, skeletal stresses are typically greatest in the first stride or two.43 Bolting from the starting gate is not what the doctor ordered, nor is barrel racing.

Incremental damage to bones. When a horse moves at speed, three forces act on a leg bone. Muscles and tendons are lifting, reaching forward, and pulling backward, bending the bone in these three directions. The hoof is making hard contact with the ground, compressing the bone. And when the hoof contacts the ground, the ground itself is restraining the hoof, counteracting the effort of muscles and tendons and bending the bones forward.

Research finds that although the stresses on a horses leg bones are enormous, they are also well below the maximum compressive strength of healthy bone.44 Feral horses likely never have dangerous stresses on their bones from running. Nor do most domestic horses.

But bone is susceptible to fatigue damage: accumulating microscopic damage caused by repetitive loading. So the more a bone has been stressed, and the more frequently the bone is stressed, the more likely it is to fail. Hairline fractures often develop into complete fractures in the absence of early detection and immediate rest. My horse G broke his ankle at the track, likely because of a hairline fracture that was treated with pain killing drugs rather than time off. Horses become dogfood when their owners push their bones too hard.

Bone fatigue is likely in racing, jumping, and endurance. In a steeplechase with 30 jumps of an average of 1.5 meters in height and distance of 7,220 meters, a typical horse would take about 1,600 strides. This is within the range of loading cycles to produce fatigue failure.45 Fractures in the long bones of race horses are significantly common,46 and many are likely induced by bone fatigue.47

Adapting for Speed or Distance. The muscles that move a horse’s legs are located high off the ground. Much of the visible leg (below the barrel) consists of bone and tendon, and this is especially true below the hock and knee. In humans, in contrast, our calf muscle is down near our foot. There are several benefits of the horse’s design.

Reduced unsprung weight — the weight below the suspension. Unsprung weight in an animal or vehicle is a handicap in acceleration, deceleration, and handling rough terrain. The weight of the wheels of a car (located below the suspension) add inertia to the suspension, and make it work harder. By moving the bulk of its weight up into the body, the horse improves his suspension and thus reduces the damage that movement can cause.

Less inertia — the tendency to not change in speed. Inertia depends on mass: a freight train is harder to start and stop than a bicycle. A heavy limb swings just fine once in motion, but requires more effort than a light limb to reverse its direction, accelerate, or decelerate. Humans have heavy legs. A horse has relatively lighter legs. And as a horse improves his conditioning, no weight is added to his visible legs.

More elastic rebound — the tendency of a muscle or tendon to return to its original position when stretched. The effect is something like the operation of a spring. Elastic rebound puts a spring in our step.

Elastic rebound is a bouncing mechanism found in humans,48 kangaroos, springhares, running birds, and trotting quadrupeds such as horses.49 Except for humans, these animals always land on their toes, rather than their heels. Human runners can land on their toes or heels. During a horse’s forward movement, his trunk rises and falls. To raise the trunk, your horse expends energy, but as it falls, he recaptures some of it: the spine flexes and limb muscles and ligaments are stretched, storing potential energy, which can be transformed to kinetic energy through elastic rebound.

A study from Italy50 found that when running on a treadmill, landing on the toes used 7-12% more energy than landing on the heels. But landing on the toes produced 25% greater acceleration. Distance runners should save their energy, and land on their heels. Sprinters need the acceleration, and should land on their toes. Why this effect? As a foot strikes the ground, tendons stretch, storing energy and absorbing shock. When the foot is lifted, the energy stored in the tendon helps lift it. By landing on the heel, the human’s leg tendons are stretched farther, storing more energy, accounting for the 7-12% energy savings. By running on their toes, humans reduce unsprung weight, reducing the handicap to their acceleration.

Leg length also affects elastic rebound. Longer legs have longer tendons that stretch farther, and so recover more energy through elastic rebound. Distance runners have long legs; sprinters have short legs.

So four factors account for why horses and antelopes are the longest distance runners of all animals: reduced unsprung weight, less inertia in the lower leg, more elastic rebound from long legs and tendons, and running on their toes.

The different designs imply that animals that land on their toes are adapted for speed, while those that land on their heels (such as elephants) are designed for efficient movement, and that humans, who can land either way, are designed for both speed and distance. The flexibility in landing style helps account for how a human can run down an antelope through persistence hunting. Pursuing it in the hottest part of the day, the upright human picks up less heat from the sun than the antelope. Hairless, the human benefits more from sweat than an antelope with its thick coat. And running by landing on his heels gives him more efficiency than the antelope. After 2 to 5 hours and up to a marathon distance, the human wears the antelope out, comes upon it exhausted, and kills it.51 An interesting review52 concludes that much in the human form suits us for endurance running, that humans are pretty good at it, and that we may have been doing it for about 2 million years.

Running under Load.

What does adding a load to your horse’s back do to him? Researchers53 who examined the effects of load on running rats, dogs, humans, and horses, testing with loads of 7 and 27% of their weight. Load did not affect stride frequency, average number of feet on the ground over an integral number of strides, the time of contact of each foot relative to the other feet, or the average vertical acceleration of the feet. They concluded that the muscular force developed by the animal increases in direct proportion to the load, and that the rate of energy expended is directly proportional to this muscular force. A heavy saddle and heavy rider will cause a horse to burn more calories than a lighter load. And calorie consumption goes up with speed.

If you think you are too heavy for endurance riding, you will be comforted by the results of research from California. Two researchers54 measured the weight, body condition score, cannon bone circumference, combined rider and tack weight, heart girth, and body lengths of 366 horses competing in one of two 160 km (100 mi) endurance races.  Rider weight and the ratio of rider weight to horse weight had no effect on overall completion rates among all horses. Among horses successfully completing the course, rider weight and rider weight ratio had no effect on finish time or placing: a conditioned horse could carry 20-30% of his weight for 100 miles. Among horses who were eliminated, rider weight and rider weight ratio had no effect on miles completed before failure. These researchers did find affects of horse condition, and concluded that condition is a very important factor in endurance performance, and is a more important factor than is the weight of the rider, or the rider weight in relation to the weight of the horse.

In a second study of those completing the 100 mile Tevis Cup,55 researchers found that the chance of finishing the event was not affected the horse’s body weight, rider weight plus tack, total ride weight (horse+tack+rider), and cannon bone circumference. But for horses that dropped out because of metabolic failure, the ratio of the weight of rider plus tack to horse weight did matter: horses failed under heavier loads. For riders who finished the course, the average weight of rider+tack was 178 lbs, with a range of 130-233 pounds. Also, and no surprise: horses who finished the Tevis Cup were in better condition than those who dropped out.

The California studies just mentioned analyzed endurance riders and horses, both of which were extremely fit. Surely if you put your entire family on your horse, it will have an affect on him. How much is too much? In a study entitled “Evaluation of Indicators of Weight-Carrying Ability of Light Riding Horses”, four researchers56 learned some interesting things. Not surprisingly, they learned that a higher work rate was required by the canter than the trot, and that the more weight a horse carried, the harder it had to work. But my surprise was the finding that when the load was about 20% of the horse’s weight or less, work rate was unaffected.

Work rate was calculated for horses carrying 15, 20, 25, or 30% of their body weight. Energy expenditure was always higher at the faster canter. These results suggest that when the load was about 20% of the horse’s weight or less, work rate was unaffected. Bars within same gait with different superscripts (a, ab, bc and a, b, c) were significantly different.57

If my mature thoroughbred now weighs 1,256 pounds58, then my own weight plus tack should be under 20% of this, or 251. If you own an “average horse”, we are told that it weighs 1,100 pounds59 — so you and your tack should be 220 or less if you don’t want to add to his strain. If you want to finish the Tevis, get your weight+tack down as much as you can. Improve his fitness or stay at a walk or trot or get a lighter saddle, and you will improve things even more. But of course, we should all think about dropping some of our weight. I think about it often.

Standing.

Horses do a lot of standing in place. They can relax their muscles, doze, and sleep while standing. Standing is a good idea if a monster might be in the bushes, ready for dinner.

Horses are able to sleep while standing by invoking a stay apparatus in their legs. In their front legs, the bone structure automatically locks the legs when they relax their muscles. In the hind legs, a stay apparatus locks the patella (knee cap) in place when the horse shifts his hips. The patella is locked in place by a hook at the stifle joint, on the inside bottom end of the femur. When engaged, it cups the patella and the middle patella ligament, preventing the leg from bending.

The stay apparatus began to develop about 5 million years ago, and was well developed 3.5 million years ago.60 There is evidence that a three-toed horse lived above the timberline of the alpine steppes of the Tibetan Plateau about 4.6 million years ago.61 Dozing while standing would have had conveyed benefit in the early detection of predators in such habitat, and would have offered quicker escapes, so there was selective pressure to make dozing while standing easy.

I’ve long wondered how it is that the stay apparatus doesn’t accidentally lock things up when the horse is moving about. The answer? When a horse is about to lift his foot, “the action of the rectus femoris muscle is replaced by that of the vastus lateralis, which prevents hooking of the patella on the medial ridge of the femoral trochlea by rotating it laterally around a longitudinal axis.62” Twist and lift. Very clever.

Jumping.

Horse jumps up with front legs, then drives with rear. Legs are outstretched during flight. The horse lands first on his front legs. A jump is something like a “bound”63

Soring.

I couldn’t bear to do all of the research for this section, so I quote from the work of the Humane Society of the United States:64

“Soring involves the intentional infliction of pain to a horse’s legs or hooves in order to force the horse to perform an artificial, exaggerated gait. Caustic chemicals—blistering agents like mustard oil, diesel fuel and kerosene—are applied to the horse’s limbs, causing extreme pain and suffering.

“A particularly egregious form of soring, known as pressure shoeing, involves cutting a horse’s hoof almost to the quick and tightly nailing on a shoe, or standing a horse for hours with the sensitive part of his soles on a block or other raised object. This causes excruciating pressure and pain whenever the horse puts weight on the hoof.

“Soring has been a common and widespread practice in the Tennessee walking horse show industry for decades.

“Tennessee walking horses, known for their smooth gait and gentle disposition, commonly suffer from the practice of soring. Other gaited breeds, such as racking horses and spotted saddle horses, also fall victim.

“The life of a sored horse is filled with fear and pain. While being sored, a horse can be left in his stall for days at a time, his legs covered in caustic chemicals and plastic wrap to “cook” the chemicals deep into his flesh. In training barns where soring takes place, it is common to see horses lying down in their stalls, moaning in pain.

“Whenever the horses are ridden, in training or competition, trainers put chains around the horse’s sored ankles. As the horse travels, the chains slide up and down, further irritating the areas already made painful by soring…”

Watch the undercover video made by HSUS.65 And visit Konovod.com,66 to see more photos. The site is in Russian, so you might want to copy text from it and paste it into translate.google.com

Terminology

There are a number of terms that relate to gait as experienced by the rider.

  • Action: Strides in which the horse lifts his feet high, flexing or bending knees and ankles.
  • Counter-canter: A canter on the wrong lead.
  • Diagonal gait: A gait in which the front foot and diagonally opposite hind foot take off and land at the same time. The trot is an example of this gait.
  • Flying lead change: Switching from one lead to the other without breaking gait, during the suspension phase of the canter.
  • Lead: At a canter or gallop, the lead refers to which rear foot reaches farther forward. When moving around a track on the correct lead, the inside front and rear legs reach farther forward.
  • Left lead canter: A 3 gait sequence in which the left hind leads the right hind. Left rear and right fore move together. The left fore lands in front of the right fore.
  • Near fore: the horse’s left front leg.
  • Near hind: the horse’s left rear leg.
  • Nearside: the horse’s left side.
  • Off fore: the horse’s right front leg.
  • Off hind: the horse’s right rear leg.
  • Pirouette: A swivel around the hindquarters, the forehand moving in a large circle and the back in a very small circle.
  • Right lead canter: A 3 gait sequence in which the right hind leads the left hind. Right rear and left fore move together. The right fore lands in front of the left fore.
  • Simple change: Changing leads while not changing gait, at walk or trot.
  • Stride: The distance covered by a horse’s foot, measured from first imprint to second imprint of a horse’s foot.
  • Track up: a hind hoof lands in the hoof print of the front hoof of the same side, or ahead of that print.

<<<<>>>>


1 image source: Ransom, Jason I., and Brian S. Cade. “Quantifying Equid Behavior–A Research Ethogram for Free-Roaming Feral Horses.” U.S. Geological Survey Techniques and Methods 2-A9, 23 p. (2009) http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1018&context=usgspubs

2 Garland, Theodore. “The relation between maximal running speed and body mass in terrestrial mammals.” Journal of Zoology 199, no. 2 (1983): 157-170.

3 Hildebrand, Milton. “Motions of the running cheetah and horse.” Journal of Mammalogy 40, no. 4 (1959): 481-495.

4 Taylor, C. Richard, Geoffrey MO Maloiy, Ewald R. Weibel, Vaughan A. Langman, John MZ Kamau, Howard J. Seeherman, and Norman C. Heglund. “Design of the mammalian respiratory system. III. Scaling maximum aerobic capacity to body mass: wild and domestic mammals.” Respiration physiology 44, no. 1 (1981): 25-37.

5 Figure this out for yourself by watching this grand slow motion video: https://www.youtube.com/watch?v=Yx3ZTdohMCc

6 Muybridge, Eadweard. “Human and Animal Locomotion, Vol. 3.” Dover Publications, Inc. New York. (1979).

7 Assessed from Plate 579. “Elberon” walking, saddled. P. 1174-1175.

8 “Ambling Gait”. Wikipedia. https://en.wikipedia.org/wiki/Ambling_gait

9 Assessed from Plate 590. “Clinton” ambling. Bareback; rider nude. P. 1196-1197

10 Assessed from Plate 591. “Pronto” pacing, saddled. P. 1198-1199.

11 Assessed from Plate 596. “Eagle” trotting, free. P. 1208-1209.

12 Assessed from Plate 615. “Hansel” cantering, bareback. P. 1246-1247

13 Assessed from Plate 625. “Bouquet” galloping. P. 1266-1267.

14 Mendik, Natalie DeFee “Horse Gaitedness: It’s in the Genes”. The Horse. April 17, 2013. Retrieved 2017-03-03/ http://www.thehorse.com/articles/31702/horse-gaitedness-its-in-the-genes?utm_source=Newsletter&utm_medium=lameness&utm_campaign=04-17-2013

15 “Horse Gaits; How the Horse moves itself”

http://petcaretips.net/horse-gaits.html

16 Muybridge, Eadweard. Animals in motion. Courier Corporation, 2012.

17 Muybridge, Eadweard. The human figure in motion. Courier Corporation, 2012.

18 Image source: https://upload.wikimedia.org/wikipedia/commons/3/32/A_horse_walking._Photogravure_after_Eadweard_Muybridge%2C_1887_Wellcome_V0048735.jpg

19 Image source: https://upload.wikimedia.org/wikipedia/commons/7/77/A_horse_trotting._Photogravure_after_Eadweard_Muybridge%2C_188_Wellcome_V0048736.jpg

20 Image source:https://upload.wikimedia.org/wikipedia/commons/4/4a/Muybridge_race_horse_gallop.jpg

21 Agricultural Communications, Texas A&M University System (5 September 2012). “‘Gaited’ Gene Mutation and Related Motion Examined”. The Horse. Blood-Horse Publications. Retrieved 2017-03-03.; Andersson, L.S., Larhammar, M., Memic, F., Wootz, H., Schwochow, D., Rubin, C.J., Patra, K., Arnason, T., Wellbring, L., Hjälm, G. and Imsland, F., 2012. Mutations in DMRT3 affect locomotion in horses and spinal circuit function in mice. Nature, 488(7413), pp.642-646.

22 Yong, Ed (2012-08-29). “One gait-keeper gene allows horses to move in unusual ways”. National Geographic. http://phenomena.nationalgeographic.com/2012/08/29/one-gait-keeper-gene-allows-horses-to-move-in-unusual-ways/ Retrieved 2017-03-03. (read the comments here to see claims of gaited horses that can gallop).

23 Wutke, S., Andersson, L., Benecke, N., Sandoval-Castellanos, E., Gonzalez, J., Hallsson, J.H., Lõugas, L., Magnell, O., Morales-Muniz, A., Orlando, L. and Pálsdóttir, A.H., 2016. The origin of ambling horses. Current Biology, 26(15), pp.R697-R699.

24 Wikipedia: “History of Iceland.” https://en.wikipedia.org/wiki/History_of_Iceland

25 Mendik, Natalie DeFee “Horse Gaitedness: It’s in the Genes”. The Horse. April 17, 2013. Retrieved 2017-03-03/ http://www.thehorse.com/articles/31702/horse-gaitedness-its-in-the- genes?utm_source=Newsletter&utm_medium=lameness&utm_campaign=04-17-2013

26 Image source: https://pixabay.com/en/horse-racing-racecourse-competition-1577287/

27 Tokuriki, M., and O. Aoki. “Neck muscles activity in horses during locomotion with and without a rider.” Equine exercise physiology 3 (1991): 146-150.

28 Margaria, R. 1938 Sulla fisiologia e specialmente sul consumo energetico della marcia e della corsa a varia velocita ed inclinazione del terreno. Atti Academia Nazionale dei Lincei Memorie 7, 299–368. cited in Rubenson, Jonas, Denham B. Heliams, David G. Lloyd, and Paul A. Fournier. “Gait selection in the ostrich: mechanical and metabolic characteristics of walking and running with and without an aerial phase.” Proceedings of the Royal Society of London-B 271, no. 1543 (2004): 1091.

29 Hoyt, D. F. & Taylor, C. R. 1981 Gait and energetics of locomotion in horses. Nature 292, 239–240.; Wickler, S. J., Hoyt, D. F., Cogger, E. A. & Myers, G. 2003 The energetics of the trot–gallop transition. J. Exp. Biol. 206, 1557–1564.

30 Image source: https://commons.wikimedia.org/wiki/File:Comparative-view-of-skeletons-of-man-and-horse-C.jpg

31 Bramble, D. M. and F. A. Jenkins Jr., in Complex Organismal Functions: Integration and Evolution In Vertebrates, D. B. Wake and G. Roth, Eds. (Wiley-Interscience, Chicester, UK, 1989), pp. 133-146.

32 Bramble, Dennis M., and David R. Carrier. “Running and breathing in mammals.” Science 219, no. 4582 (1983): 251-256.; Bramble, Dennis M., and Farish A. Jenkins Jr. “Mammalian locomotor-respiratory integration: implications for diaphragmatic and pulmonary design.” Science 262, no. 5131 (1993): 235-240.; Young, Iain S., Ruth D. Warren, and John D. Altringham. “Some properties of the mammalian locomotory and respiratory systems in relation to body mass.” Journal of Experimental Biology 164, no. 1 (1992): 283-294.

33 Bramble, Dennis M., and David R. Carrier. “Running and breathing in mammals.” Science 219, no. 4582 (1983): 251-256.

34 Bramble, Dennis M., and Farish A. Jenkins Jr. “Mammalian locomotor-respiratory integration: implications for diaphragmatic and pulmonary design.” Science 262, no. 5131 (1993): 235-240.

35 Alexander, RMcN. “On the synchronization of breathing with running in wallabies (Macropus spp.) and horses (Equus caballus).” Journal of Zoology 218.1 (1989): 69-85.

36 Young, Iain S., R. Alexander, A. J. Woakes, P. J. Butler, and L. Anderson. “The synchronization of ventilation and locomotion in horses (Equus caballus).” Journal of Experimental Biology 166, no. 1 (1992): 19-31.

37 Hildebrand, Milton. “Motions of the running cheetah and horse.” Journal of Mammalogy 40, no. 4 (1959): 481-495.

38 Alexander, RMcN. “On the synchronization of breathing with running in wallabies (Macropus spp.) and horses (Equus caballus).” Journal of Zoology 218.1 (1989): 69-85.

39 For information that pacing horses don’t well synchronize respiration and stride, and may fatigue faster than a galloping horse as a result, see Evans, D. L., E. B. Silverman, D. R. Hodgson, M. D. Eaton, and R. J. Rose. “Gait and respiration in Standardbred horses when pacing and galloping.” Research in veterinary science 57, no. 2 (1994): 233-239.

40 Image source: Lafortuna, Claudio L., Emanuela Reinach, and Franco Saibene. “The effects of locomotor-respiratory coupling on the pattern of breathing in horses.” The Journal of physiology 492.Pt 2 (1996): 587.

41 Griffin, Ashley and Christine Skelly, “Natural and Artificial Gaits of the Horse”. My Horse University. http://myhorseuniversity.com/resources/eTips/April_2011/Didyouknow

42 Lafortuna, Claudio L., Emanuela Reinach, and Franco Saibene. “The effects of locomotor-respiratory coupling on the pattern of breathing in horses.” The Journal of physiology 492, no. Pt 2 (1996): 587.

43 Biewener, A. A., J. J. Thomason, and L. E. Lanyon. “Mechanics of locomotion and jumping in the horse (Equus): in vivo stress in the tibia and metatarsus.” Journal of Zoology 214, no. 3 (1988): 547-565.

44 Reviewed in Currey, John D. “The mechanical properties of bone.” Clinical Orthopaedics and Related Research 73 (1970): 210-231.

45 Biewener, A. A., J. J. Thomason, and L. E. Lanyon. “Mechanics of locomotion and jumping in the horse (Equus): in vivo stress in the tibia and metatarsus.” Journal of Zoology 214, no. 3 (1988): 547-565.; Carter, Dennis R., William E. Caler, Dan M. Spengler, and Victor H. Frankel. “Fatigue behavior of adult cortical bone: the influence of mean strain and strain range.” Acta Orthopaedica Scandinavica 52, no. 5 (1981): 481-490.

46 Currey, J. D. “What is bone for? Property-function relationships in bone.” Mechanical properties of bone. New York: American Society of Mechanical Engineers. p (1981): 13-26.

47 Biewener, A. A., J. J. Thomason, and L. E. Lanyon. “Mechanics of locomotion and jumping in the horse (Equus): in vivo stress in the tibia and metatarsus.” Journal of Zoology 214, no. 3 (1988): 547-565.

48 Cavagna G. A., Heglund N. C., Taylor C. R. 1977 Mechanical work in terrestrial locomotion: two basic mechanisms for minimizing energy expenditure. Am. J. Physiol. 233, R243–R261

49 Cavagna G. A., Heglund N. C., Taylor C. R. 1977 Mechanical work in terrestrial locomotion: two basic mechanisms for minimizing energy expenditure. Am. J. Physiol. 233, R243–R261

50 Ardigo, L. P., C. Lafortuna, A. E. Minetti, P. Mognoni, and F. Saibene. “Metabolic and mechanical aspects of foot landing type, forefoot and rearfoot strike, in human running.” Acta Physiologica Scandinavica 155, no. 1 (1995): 17-22.

51 Persistence hunting has allowed humans to capture cheetahs. See “Persistence Hunting”

https://en.wikipedia.org/wiki/Persistence_hunting and see a video in which this is done: David Attenborough’s documentary The Life of Mammals (program 10, “Food For Thought”) https://www.youtube.com/watch?v=826HMLoiE_o

52 Bramble, Dennis M., and Daniel E. Lieberman. “Endurance running and the evolution of Homo.” Nature 432, no. 7015 (2004): 345-352.

53 Taylor, C. Richard, Norman C. Heglund, Thomas A. McMahon, and Todd R. Looney. “Energetic cost of generating muscular force during running: a comparison of large and small animals.” Journal of Experimental Biology 86, no. 1 (1980): 9-18.

54 Garlinghouse, Susan E., and Melinda J. Burrill. “Relationship of body condition score to completion rate during 160 km endurance races.” Equine Veterinary Journal 31, no. S30 (1999): 591-595.

55 Garlinghouse, S. E., R. E. Bray, E. A. Cogger, and S. J. Wickler. “The influence of body measurements and condition score on performance results during the 1998 Tevis Cup.” In Proceedings 16th Equine Nutrition and Physiology Society Symposium, pp. 398-402. 1999.

56 Powell, Debra M., Karen Bennett-Wimbush, Amy Peeples, and Maria Duthie. “Evaluation of indicators of weight-carrying ability of light riding horses.” Journal of Equine Veterinary Science 28, no. 1 (2008): 28-33.

57 Image source: Powell, Debra M., Karen Bennett-Wimbush, Amy Peeples, and Maria Duthie. “Evaluation of indicators of weight-carrying ability of light riding horses.” Journal of Equine Veterinary Science 28, no. 1 (2008): 28-33.

58 “How much does a racehorse weigh?” https://www.reference.com/pets-animals/much-racehorse-weigh-9764f37cf20f6193#

59 “How much does an average horse weigh?” https://www.reference.com/pets-animals/much-average-horse-weigh-289a0e909645d02d?qo=contentSimilarQuestions

60 Hermanson, John W., and Bruce J. Macfadden. “Evolutionary and functional morphology of the shoulder region and stay-apparatus in fossil and extant horses (Equidae).” Journal of Vertebrate Paleontology 12, no. 3 (1992): 377-386.

61 Deng, Tao, Qiang Li, Zhijie Jack Tseng, Gary T. Takeuchi, Yang Wang, Guangpu Xie, Shiqi Wang, Sukuan Hou, and Xiaoming Wang. “Locomotive implication of a Pliocene three-toed horse skeleton from Tibet and its paleo-altimetry significance.” Proceedings of the National Academy of Sciences 109, no. 19 (2012): 7374-7378.

62 Wentink, G. H. “Biokinetical analysis of the movements of the pelvic limb of the horse and the role of the muscles in the walk and the trot.” Anatomy and embryology 152, no. 3 (1978): 261-272.

63 See the animation at http://members.casema.nl/gertvandijk/walking/quadrupeds.htm#

64 “What is Soring?” Important facts about this cruel abuse. the Humane Society of the United States. Retrieved from http://www.humanesociety.org/issues/tenn_walking_horses/facts/what_is_soring.html on March 3, 2017.

65 “Tennessee Walking Horse Investigation Exposes Cruelty” The Humane Society of the United States. https://www.youtube.com/watch?v=gxVlxT_x-f0

66 http://konovod.com/index.php?id=1279

 

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