Exercise Physiology and the Performance Horse
By Richard G. Godbee, Ph.D., PAS, Dipl. ACAS-Nutrition
Most horses at one time or another are used for some type of athletic activity. This includes halter, endurance, racing and working horses. Regardless of the discipline, every horse requires energy to fuel muscle activity. Athletic performance (exercise) may be classified into three general types. During training and/or competition, horses may experience each of these alone or in combination. These may be classified as:
- Speed or sprint type of activity. This is usually less than 440 yd, 1 minute in duration, and maximum exertion (VO2 max). This type of exercise is fueled by anaerobic metabolism. Disciplines included are Quarter Horse racing, barrel racing, timed events, and draft horse pulls, where heart rates exceeding 160-180 beats per minute, which is thought to be the anaerobic threshold. Depending on the physical conditioning of the horse, this occurs at speeds of 11-22 miles per hour. Glucose is the primary fuel.
- The second type of exercise may be classified as middle distance. This includes race distances of 0.5 to 2 miles lasting several minutes in duration, and 75-95% VO2 max which combines anaerobic and aerobic metabolism. Thoroughbred and Standardbred racing are examples. Up to a given point, these horses will be performing aerobically, changing to anaerobic metabolism as time and distance increase. Horses may use fats and glucose as the primary fuels for this type of muscle activity.
- Endurance, often referred to as sub-maximal exercise, lasts for over 2 hours and relies primarily on aerobic energy production. Competitive and endurance riding, ranch work, farming and even school horses fit in this group. Aerobic metabolism is more energy efficient and allows for energy production from fats, protein, and liver and muscle glycogen.
Many disciplines require a combination of these types of metabolism while the event is taking place. Cutting, polo, and working cow horse, for example, require a combination of each. Show jumpers require middle distance and sprint type activity. All athletic activities will utilize aerobic metabolism if only for warm-up and cool down.
Anaerobic metabolism is less efficient than aerobic both in choice of fuels and end product produced. During anaerobic metabolism, muscle and liver glycogen serve as the primary energy source. Body stores of both are relatively small, so depletion occurs quickly. Another issue of anaerobic metabolism is the incomplete combustion of glucose resulting in the accumulation of lactic acid. Lactic acid lowers the pH in the muscle, which further inhibits metabolism and muscle function. The rate or speed that lactic acid accumulates relates directly to how quickly a horse slows down, an example is slowing at the end of a flat track race. Aerobic metabolism allows dietary and body fat to be used as energy with CO2 and water being the end products. In most horses, body stores of fat far exceed that of liver and muscle glycogen levels. It has been suggested that a horse may produce 600 times more energy from energy sources in the body during aerobic compared to anaerobic metabolism.
Proper conditions for the chosen discipline or activity are critical to maximize the horse’s ability to succeed. The more fit the horse, the more efficient it is in energy utilization. In order to efficiently utilize the increase in dietary energy, additional nutrients may be required. Increased dietary vitamin E to serve as an antioxidant along with more dietary B-vitamins is often added to the ration through proper supplementation.
The Vita Flex edge:
Breeding coupled with training, a little bit of luck and proper nutrition all play an integral part in any athletic success. Vita Flex makes products designed to help give competitors the competitive edge. This includes products, such as Lactanase® supplement, which supports optimal muscle function and metabolism in the horse by releasing energy from both carbohydrates and fats. As mentioned previously, competitive riders will benefit from making sure their horse can utilize the increased dietary energy by making sure their horse is getting the proper nutrients. Accel® Lifetime supplement is a unique blend of ingredients which includes vitamins E and B6. Accel® Lifetime supplement also includes 14 amino acids to maintain muscle tissue and prevent protein breakdown during athletic activities.
Accel and Lactanase are registered trademarks of Farnam Companies, Inc.