Photo: Thinkstock

Over the ages horses have developed into excellent athletes. They have many unique adaptations that facilitate their ability to exercise. For instance, horses have a huge mass of skeletal muscle that is well adapted to long-distance exercise; they have a reserve blood supply to support oxygen carriage during exercise; and their ability to increase their heart rate and overall oxygen uptake almost eight-fold from rest is incredible compared to that in many other animals. This athleticism has made horses so useful to humans over the years, for work and for transport.

Recently, however, the horse has been primarily used for sport and pleasure purposes. While obviously our elite equine athletes are a significant part of the horse industry, their contribution to overall horse population is small compared to those horses used for pleasure. There are a good number of horses competing on a national and local level that are primarily sport animals, but many of these horses are still “pets” to their owners and serve a dual purpose. The largest population of horses falls in the pet-pleasure category—horses ridden for pleasure, maybe with a few shows thrown in, but primarily companion animals. This population of animals appears to be most at risk for obesity, though some disciplines reward horses with “extra condition.”

Regardless of use or body condition, most horses could be exercised more. Assuming the animal is sound, it should be worked almost daily. This is especially important for overweight animals as exercise will increase the daily calorie expenditure more rapidly. Increased exercise combined with reduced calorie intake will hasten weight loss. Unfortunately, riding a horse at a decent level of work effort (either the length time of the ride, the frequency of the rides per week, or the intensity of a given ride) is time consuming and difficult for many horse owners to accomplish.

Health Benefits

Even for non-obese horses, exercise is extremely important for overall health. Not all horses, however, need to be ridden every day; some benefit from being lunged or worked in a round pen and others (especially older horses) do well with just free exercise in a large pasture (or dry lot). Nonetheless, exercise is extremely beneficial for a horse’s overall health.

Exercise works many systems in the horse’s body, most notably the cardiovascular, respiratory, skeletal, and muscular systems. Exercise causes an increase in heart rate, increased cardiac output (the amount of blood pumped per minute), and increased respiration, challenging the body systems to adapt and become more efficient.

Skeletal bone is not a dead tissue; it is constantly being remodeled through the removing and depositing of calcium and phosphorus. Weight-bearing exercise stimulates remodeling and builds stronger bones. The muscle generates forces for movement and is highly adaptive to the stresses put to it. A horse trained for endurance types of exercise develops muscles more suitable for that type of work while a horse trained for high-intensity sprints endures muscular changes to fit those challenges. (It should be noted there are some genetic predispositions to the type of work a horse is most suited for; such as Quarter Horses being sprint animals and Arabians being endurance mounts.) In addition, exercise, particularly free exercise at pasture, is especially important for the overall mental well being of an animal.

Exercising obese horses has additional benefits. For instance, the calories burned during exercise can offset any required reductions in caloric intake and, therefore, you may not have to limit your horse’s feed drastically. Alternatively, you can speed up the weight-loss effort through a combination of diet and exercise.

Exercise also has several metabolic benefits for obese horses. Because skeletal muscle is the largest user of glucose in the body, particularly through insulin stimulation, increasing the mass of skeletal muscle can greatly increase insulin sensitivity. Furthermore, exercise increases the number of glucose transporters (specifically the GLUT4 type that are insulin-sensitive to help move glucose across a cell membrane [Stewart-Hunt et al., 2006]). Thus, exercise not only increases the total quantity of insulin-sensitive tissue, namely skeletal muscle, but also increases the muscle’s ability to use it. Several research studies have found a direct increase in insulin sensitivity through physical conditioning (Pratt et al., 2006; Stewart-Hunt et al., 2006). Exercise alone is often not enough, though; research in humans shows that adipocytokines (leptin and adiponectin) are only affected when exercise is accompanied by weight loss (due to adipose tissue loss).

In a practical example, Pagan and coworkers (2009), who examined body condition scores and insulin dynamics in sport horses, reported that pony hunters had significantly higher body condition scores than horses in other disciplines (such as show hunters or dressage horses). These ponies however had low incidence of hyperinsulinemia (only 8% of the ponies, compared to 50% of ponies with body condition score greater than 7 reported by Carter et al., 2009), suggesting a protective effect of exercise, even in light of excess adipose tissue.