The natural athleticism of the horse is due in large part to the amazing anatomy of its heart. A horse has a specialized circulatory system that supports the huge oxygen demands of its outsized muscles.
The heart of an adult horse at rest pumps out about 10.6 gallons (25-40 L) of blood per minute (compared to the relatively meek average resting human’s 1-1.3 gallons (4-5 L) per minute). During a hard workout, your horse’s heart can pump 79 gallons (300 L) per minute!
In horses, as in humans, the greater the volume of blood pumped quickly around the body, the more oxygen it can pick up from the lungs for transport to the hard working muscles.
The amount of blood pumped by a horse’s heart increases incredibly quickly and substantially during a workout, making the horse one of the most highly adapted aerobic athletes!
You can learn more about how to adapt your training routine to the amazing abilities of your horse's heart here.