According to the Guinness Book of World Records, the fastest recorded speed of a racehorse was achieved by Winning Brew who clocked 43.97 mph (70.76 km/h) in 2008. That’s fast. That’s very fast.
So, why do horses run so fast? And how can horses run so fast? We’re going to answer these questions by looking at how horses evolved, the psychology that leads them to run so fast, and the physiology and anatomy that makes it possible.
Why Do Horses Run So Fast: The Psychology Behind Running For Your Life
The modern horse (called the Equus Caballus) has taken 60 million years of evolution to reach its current form. It started as the Eohippus, an ancient ancestor of the modern horse which was much smaller – just 14 to 15 inches tall – roughly the size of a fox. During this evolution, the horse has adapted to changing environments and predators.
For instance, the modern horse is larger, stronger, and can run faster than all of its ancestors. These are all adaptations that have helped the horse survive in the wild.
Horses run for many reasons from getting exercise to having fun and from being excited and in a race. But why do horses run so fast?
One of the main reasons why horses run so fast is because they have to. In the wild, horses are prey animals. This means that they are constantly being hunted by predators. Speed equated survival.
In order to survive, horses have had to evolve to be able to run very fast. Along the evolution trail, those forms of horses that evolved into fast runners survived while the rest became extinct. For the same reason, horses also became long distance runners.
This evolution led to the animal family Equidae which includes modern horses, zebras, asses, donkeys, and the Mongolian wild horse (also known as Przewalski’s horse).
How Do Horses Run So Fast? – The Legs, Joints, Feet and Hooves
The primary body parts that allow a horse to run so fast are its legs, joints, feet and hooves.
Horses have long legs in proportion to their bodies. This allows them to take longer strides and run faster. Interestingly, a horse’s legs have no muscles below the knee. And so long tendons connect the thigh muscles to the feet.
While this structure puts enormous stress on the legs (sometimes during a gallop the horse’s entire weight is borne by a single leg), it gives great freedom of movement to the joints and the thin legs are lighter for speed and can be more easily moved.
A horse’s feet and hooves are also specially adapted for speed and endurance. The hoof – which we can say is the equivalent of a bird’s claw or a human nail – is circular but has an opening giving it a crescent shape. In the opening is the heel.
The heel is flexible while the hoof walls are not. This way the hoof walls can bear the horse’s weight while the flexible heal can allow for slight changes to the hoof’s shape helping it handle changes in weight as well as the angle at which the weight falls on the hoof.
These adaptations to the foot and heel allow the horse to run on almost any surface and maintain speed and agility even when running on uneven ground.
Respiration and Circulation That Make It Possible
A horse’s respiration and circulation systems are also specially adapted to allow for speed and endurance. The respiratory and circulatory functions work together. The respiratory extracts oxygen from the air the horse breathes and the circulatory system ensures that the oxygen is delivered to the body’s cells.
As a prey animal, the horse may need to suddenly start running from a resting position. This means the horse’s muscles may have a sudden need for oxygen. The role of the horse’s spleen in this process is often under-looked.
The horse’s spleen has evolved to store extra red blood cells. When the horse starts running suddenly or during periods of intense effort, the spleen contracts and puts the extra red blood cells into circulation. This allows more oxygen to reach the horse’s muscles just when they need it.
The Bottom Line
So, why do horses run so fast? First, because they need to. And second, because they can.
Horses are prey animals and so the need to run fast is a survival mechanism. And the physical adaptations of the horse’s legs, joints, feet and hooves as well as its respiration and circulatory systems have all evolved to allow the horse to run fast and for long periods of time.
Being able to run fast not only saves the horse from predators but also allows it to roam widely in search of food and water.
