Dogs’ Sprint Metabolism
Dogs can generate large amounts of energy for a short period of time. A dog’s heart and lungs are oversized relative to its body and its normal everyday needs. A dog also has relatively more red blood cells than a human. Most of the time the dog will keep the extra red blood cells stored in its spleen. When the animal enters into a situation where its full metabolism is required, such as play, catching game, or fighting other dogs, the extra cells are released into the bloodstream. The "oversized" heart and lungs will now be running at full capacity, and the animal will have an enhanced ability to engage in aerobic activity. This activity will produce internal heating. Dogs, being covered in fur, are limited in their ability to cool down. After a short time the animal must either cease its athletic activity or risk harming itself from overheating. One can easily observe this pattern of intense activity followed by rest periods in puppies. During the rest phase the spleen collects red blood cells and the animal may pant to cool down.
