One of the reasons the horse is such an incredible athlete is due to its heart. The equine heart is very efficient compared to humans and many other animals, and has a larger range of beats per minute (bpm) compared to humans. An elite equine’s heart rate can range from a resting 30 bpm to 250 bpm during maximal exercise. However it is also the horse’s ability to quickly drop from racing heart rate to resting heart rate which makes it unique.
Another example of efficiency is the amount of blood it can pump around the body in a short space of time. At rest an elite racehorse can pump up to 35 litres of blood around the body in one minute, while humans only pump 5 litres. Although humans are smaller than horses and therefore do not need quite as much blood to be circulated, this is still a huge difference and highly impressive.
The heart is only one cog in the system however. Horses have enormous lungs which can suck in up to 15 litres of air in one breath during moderately strenuous exercise. Keep in mind horses only ever breathe through their nostrils even at full pace. These huge lungs provide oxygen to the heart, and the heart in turn pumps oxygenated blood to the skeletal muscles and the rest of the horse's body.
This last element is not just important for the horse’s mobility and functionality, but also because the locomotion driven by the skeletal muscles is connected to breathing pattern. This locomotion has an impact on the efficiency of respiration, for example during canter and gallop the horse takes one breath per stride. Therefore the more efficient the locomotion or stride, the more efficient the respiration and vice versa.
Some people speculate that the bigger the heart the faster the horse. Thoroughbreds do have proportionally larger hearts, while draught horse’s are proportionally smaller. Famous horses such as Phar Lap and Secretariat had unusually large hearts even for thoroughbreds. However heart size alone cannot guarantee the athletic potential of a horse.
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