The horse has muscles in every part of its body. Short, thick muscles provide short bursts of speed, and long, lean muscles are needed for both speed and endurance.
FIGURE 9.4: The Muscles of the Horse
Muscles in the horse are classified as cardiac, smooth, or skeletal. Cardiac muscles involve the heart and operate involuntarily. Smooth muscles also are involuntary and involve specific functions such as digestion, breathing, and circulation. The skeletal muscles involve the horse's voluntary movements.
The contraction of muscles causes the production of lactic acid. Muscle fatigue results when there is too much of a buildup of lactic acid. Proper conditioning allows the horse to increase the muscles' ability to cope with lactic acid.
Skeletal muscles are made of different types of fibers, generally classified as slow-twitch and fast-twitch. Horses with more slow-twitch muscle fibers tend to possess greater endurance, while horses with more fast-twitch fibers typically display greater bursts of speed. Muscle makeup is one reason why certain breeds of horses are better suited to some tasks than others.
Like any athlete, horses need to be conditioned for the type and amount of riding you plan to do. Slow, simple, and step-by-step buildup is the key to adequate muscle conditioning. Dressage training provides a good foundation for any kind of riding for precisely this reason — it slowly prepares and conditions the horse's body for more complex maneuvers as it progresses from one level of training to another.
If you plan to enter your horse in, say, a twenty-five-mile competitive trail ride in August, spend a few months getting her into shape for the task, giving her muscles a slow buildup for strength and endurance. Proper conditioning is the best way to avoid long layoffs from strained muscles, tendons, and ligaments.
Also, be sure the equipment fits properly. For example, when saddles fit poorly, they contribute to bruising and straining of the longissimus dorsi muscle, which runs almost the entire length of the horse. Simply translated, this can create a sore back and result in behavioral problems if the horse hurts every time you ride it.