11/10/2025
Muscle Facts
Brian S. Burks, DVM
Diplomate, ABVP
Board Certified in Equine Practice
1. Muscles are divided into three types: smooth, cardiac, and skeletal. Smooth muscles are the involuntary muscles in your gut, blood vessels, and elsewhere that work without conscious thought. Cardiac muscles are in the heart.
Skeletal muscles are attached to bone and help with everyday activities ranging from standing to walking to running. They help the horse get up and down.
2. The horse’s body contains more than 700 muscles
These include the muscles in the limbs, as well as muscles deep inside the body, like the one that keeps the heart beating and those that help digest food. By comparison, the equine body has 205 skeletal bones.
3. Muscles are made up of special cells called muscle fibers
Their main quality is contractibility, which means the muscles can shorten or lengthen as needed. Almost all movement in the body happens because of muscle contractibility.
4. The largest muscle in the body is the gluteus maximus
It is the main extensor muscle of the hip, and it is the large muscle in the rump. It is the largest muscle in the body because its main job is to support the torso and maintain proper posture. The gluteus maximus is the main muscle used to propel the horse forward.
5. The smallest muscles in the body are in the inner ear
They include the tensor tympani and the stapedius. They connect to the eardrum and hold the inner ear together. The smallest bones in the body are also in the ear.
6. The strongest muscle, based on its size, is the masseter
It is a muscle in your horse’s jaw. It can close the teeth with great force, as is needed for the horse to crush and grind hay and grain.
7. Muscles are attached to bones by tendons
Understanding the difference between tendons and ligaments can be confusing. In addition to attaching muscles to bones, tendons also attach muscles to parts of your horse’s body such as your eyeballs. Ligaments connect one bone to another around joints.
8. Muscles make up about 40 percent of total body weight in most vertebrates.
9. The hardest working muscle in the body is the heart.
10. Some of your busiest muscles are those controlling eye movements
These muscles are constantly adjusting as the horse looks around.
11. Most of the heat produced in the body comes from muscle contraction
Muscle movement counts for almost 85 percent of the total heat produced inside the body. When your horse is cold, muscles contract involuntarily, trying to warm the body.
12. The motor cortex on one side of the brain controls muscle movement on the opposite side of the body.
The motor cortex on the right side of the brain controls the muscles on the left side of the body, while the motor cortex on the left side controls the muscles on the right side.
The brain sends movement signals through the spinal cord and out through the peripheral nervous system in your horse’s muscles. The messages from the brain become more complex when there are more muscles involved in an activity.
13. Muscles usually work in pairs
When one shortens, its corresponding muscle lengthens. Think about doing bicep curls. When you curl your arm up so the bicep is shorter, the tricep on the other side of your arm is straightened out.
14. Muscles cannot push. They can only pull.
When you’re pushing a door open, for instance, your muscles are actually pulling your elbow and shoulder against the door.
No matter what your horse is doing, muscles are at work. To keep them healthy, they need exercise. Even your heart needs a workout to stay strong, which is why aerobic exercise that gets your horse’s heart rate up is so important.
The muscles in your horse’s limbs and elsewhere need exercise, too. With aging, muscle mass is lost, but if you exercise muscles that process can be slowed and maintain a mighty muscular system for a long time. And that’s a fact.
Fox Run Equine Center
www.foxrunequine.com
(724) 727-3481
