Your horse is an amazing athlete, and it’s no surprise. Horses have evolved with amazing adaptations that allow them to run and jump faster than humanly possible. Here are a few reasons that make horses amazing athletes…

1. They blood dope themselves

Horses can instantly increase the number of red blood cells with the contraction of their spleen.

Horses can instantly increase the number of red blood cells with the contraction of their spleen.

Blood doping is common in some sports – athletes use things like erythropoietin to increase the oxygen carrying capacity of the blood, which improves their aerobic ability and stamina. Not so with horses – they have an amazing spleen which stores up to one-third of their total red blood cell volume. When they get excited, or during exercise, the spleen contracts, mobilizing the all those extra red blood cells and increasing the horse’s ability to escape danger or perform. The size of the spleen is random, too. Big horses can have small spleens, and little horses can have big spleens, and the volume of blood contained within the spleen is correlated with its weight.

2. They can breathe better than you

If you stretched the lungs out, they'd equal about the area of a tennis court.

If you stretched the lungs out, they’d equal about the area of a tennis court.

When you’re galloping at 40km/h oxygen gets used up fast. Every muscle has a massive demand for that key ingredient – oxygen. Energy can be created without oxygen, but this is expensive for the body and leads to a build-up of lactic acid (cramps, ouch!). To keep the oxygen coming, the healthy horse has a massive area for gaseous exchange – about the size of a tennis court. The total lung volume in a 500kg horse is around 40 liters – compare that with the human’s average of 6-7 liters! An average 500kg Thoroughbred might breathe about 50-60 liters per minute at rest, and about 700 liters (140ml/min/kg) per minute at maximum.

3. They defy basic physiological rules

Face it, horses have better hearts. Photo by Cheryl.

Face it, horses have better hearts. Photo by Cheryl.

The general rule is that the larger the animal, the lower the resting heart rate. Horses are bigger than us, and they have a resting heart rate that’s about half of ours. Another rule is that the larger the animal, the lower the maximal heart rate. This is where horses break the rules. They have a maximal heart rate of about 240bpm – that means they can increase their heart rate by nearly ten times above resting. Humans can only manage about four times above resting values, making horses the superior athlete.

4. They couple their breathing to their stride

And... breathe in! photo by Cathy

And… breathe in! photo by Cathy

At canter and gallop, horses breathe once per stride (except sometimes when swallowing, during acceleration or changing leads). Think of when you run – when you’re struggling you might be inclined to breathe in a quick, shallow panting pattern. Not so for the horse, and there are several theories that explain this respiratory-locomotory coupling. One is the piston-pendulum mechanism: when the horse’s front legs hit the ground at the gallop, its insides push up against the lungs, expelling the air. When the forelimbs are raised, the scapula is brought forward, this opens up the rib cage and the horse can breathe in. The other theory is that each breath is each breath is generated by the respiratory system itself, and some horses have been seen to take one breath over two strides when they have a blockage in their airways. It’s still an incredible, athletic quality.

5. Their tendons are working near breaking point

Hyperextension of the hind limb fetlock after landing from a fence.

Hyperextension of the hind limb fetlock after landing from a fence.

Ever watched a horse land from a jump in slow motion? Check out the forelimbs. When a horse lands from a jump, gallops or performs collected work, it’s the tendons and ligaments in their distal limb (from the knee down) that take the brunt of the force. The deep digital flexor tendon, superficial digital flexor tendon and suspensory ligament are designed to hold the many bones of the distal limb in line, and also serve to store energy for locomotion. It’s comparable to our Achilles tendon, but horse’s have really maximized the potential of their tendons – the efficiency of movement of the horse at a gallop is in excess of 100%. This means that they can store incredible amounts of energy, stretching tendons and ligaments to their maximum, on every stride. This is also their downfall, because with every maximal strain, there comes a little bit of damage. When tendons and ligaments are damaged, even just a little bit, they become weaker, predisposing the horse to an injury.

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