Dogs are built to go the extra mile
© Kevin Bryson/Leaping Lizzards
Most dogs, it seems, are born to run. They can run for long periods of time and over long distances.
What makes them so well adapted for running? Lots of things!
A body built for breathing...
As a dog runs, its body works like a bellows. Like other four-legged animals, a galloping dog takes
one breath with each stride (the distance between successive footfalls of the same foot). When its
back extends, it's easy for the lungs to expand and the dog inhales. When its back flexes, the lungs
are compressed, squeezing out air, and the dog exhales.
The long, lean legs of many dogs make running a breeze because it takes relatively little energy to
pump them back and forth. Dogs with the longest legs relative to their body size are usually the
fastest runners because they take the longest strides. Dogs with shorter, squat legs are usually not
very fast runners.
...a hard working heart...
Hard-working muscles need lots of oxygen. Without that extra oxygen, muscles tire and begin to
ache, causing both dogs and us to slow down. When dogs run, their heart rate skyrockets, pumping
oxygen-rich blood to the muscles. In fact, a snoozing dog has a heart rate about the same as a resting
human, 80 beats per minute. A working dog's heart rate can reach 274 beats a minute, almost double the
rate of a healthy, active human. No wonder dogs can keep going after most people are exhausted!
...and a super spleen!
Red blood cells, made in the spleen, carry oxygen throughout the body. An exercising dog dumps
extra red blood cells into its bloodstream, increasing the amount of oxygen in its blood. This helps
prevent muscle fatigue.
When dogs rev up, they pant to cool down
Like all mammals, dogs can overheat when they exercise. Because too much heat damages body systems,
mammals need a way to get rid of excess heat. Humans sweat. Dogs pant.
Have you ever held your hand in front of a panting dog's mouth? Whew -- dog breath is hot! What you
feel is excess heat leaving the dog's body.
An overheated dog breathes in and out through its mouth. With each pant, dogs inhale cool air. As
the cool air moves into the lungs, it absorbs heat and moisture. When dogs exhale hot breath across a
wet tongue, water evaporates, cooling their bodies. To maximize heat loss, panting dogs direct warm
blood to their tongue to be cooled. The hot, moist air the dog exhales is some 10°F warmer than
if it exited the nose, helping to rapidly dump body heat. But just like sweating, panting cools by
evaporation, and a panting dog needs access to plenty of drinking water.
...and cool dogs...
Unless it's a really hot day, a resting dog doesn't generate excess body heat. A resting dog
breathes normally, in and out through its nose. Inhaled air is warmed and moistened by passing through
the nose on its way to the lungs. On the reverse trip, exhaled air returns some of its warmth and
water to the body as it flows through the previously cooled nose. Breathing in and out through the
nose preserves body fluids and heat, keeping the dog hydrated and warm.
...and somewhere in between.
Dogs that are only slightly hot will breathe in the nose and out the mouth. This helps reduce water
loss. To breathe in one way and out another, dogs use their tongues to direct air-flow. The rhythmic
movement of a panting dog's tongue matches its breathing. When the tongue moves backwards, it keeps
air from traveling between the mouth and lungs and the dog inhales through the nose. As it moves
forward, it allows air to move out through the mouth. With the tongue back the dog will inhale, with
the tongue forward the dog will exhale -- all of this happening at least 5 times a second!
In the wild
© Monty Sloan/Wolfpark.org
Wild dogs run to avoid predators and to catch prey. Some wild
canines like wolves and African wild dogs will chase prey over long distances, tiring their prey
out before moving in for the kill.
Here at home: sled dogs
© Sue and Mark Hamilton
Many domestic dogs rely on this incredible endurance to work as
racers, herders, and hunting companions. Sled dogs are famous for their
ability to run over long distances, pulling the weight of their human handler and sled
behind them. In fact, the main factor limiting a racing sled dog is the number of calories
it needs and how fast it can gobble these up!