Horses running at full speed are truly impressive, showcasing incredible velocity. Even just riding a galloping horse gives you a sensation of rapid movement, but racehorses can reach speeds of up to 60–70 km/h while carrying a rider.
So, what enables horses to run so fast? Is it simply their large bodies and long legs? Here, we’ll explore the fascinating body features that make horses swift.
The Evolution of a Single Middle Finger: A Key to Speed
Herbivorous animals like horses are prey animals in the wild. To survive in harsh environments, they must be able to run fast and escape predators.
Animals, including humans, have evolved according to their environments. Horses have developed specific features to increase speed. For example, their limbs. Longer limbs allow covering more ground per stride, enabling faster movement.
Horses have evolved to support their long limbs with only their longest middle finger among the four toes, which has gradually degenerated into the hoof we see today.
Interestingly, when they run, horses’ hooves don’t touch the ground with the heels. This is similar to humans, who tend to lean forward slightly to reduce ground contact and run faster.
Thus, horses have undergone significant evolution to acquire their current hooves, optimized for speed.
The Role of Joint Movement in Speed
The limbs of horses are used mainly for walking and running. Unlike humans, they don’t need to twist or move their limbs in complex ways. Simple movement and limited joint motion actually help horses generate more stable and powerful strides, increasing speed.
In contrast, complex joint movements can cause injuries when forcefully pushing off the ground at full speed, which is dangerous. Leg injuries can be fatal for horses, as each leg supports a massive weight of 100–150 kg for a typical racehorse weighing 450–500 kg.
Horses cannot simply stay still during recovery, because their secondary pump functions are in their calves, which act as a ‘second heart’ to support blood circulation. Excessive weight bias or prolonged lying down can cause circulatory issues and hoof inflammation, so their leg structure, though seemingly restrictive, is optimized for their survival and speed.
A Larger Heart Means a Faster Horse
Racehorses that can reach incredible speeds often have larger hearts as well as more developed movements, supported by training and muscle development. There’s an even less visible difference: the size of their hearts. While a human heart weighs about 300 grams, a horse’s heart can weigh 4–5 kg.
Considering proportional differences, human hearts make up about 0.4-0.5% of total body weight in a 50-60 kg person, but for horses weighing 400–500 kg, their hearts account for about 1.0% of their body weight.
Top athletes in human sports often have larger hearts due to training. Horses’ large hearts are built to endure the high heart rates during intense exercise. The more powerful a racehorse’s cardiovascular system, the faster they can run, demonstrating size and strength in their hearts.