Risk Factors for Elimination During Endurance Rides Examined

Risk Factors for Elimination During Endurance Rides Examined

The most common reasons for elimination from endurance competitions were lameness and metabolic problems.

Photo: Anne M. Eberhardt/The Horse

Endurance rides covering distances from 40 to 160 kilometers in a 24-hour period are grueling tasks for both horse and rider. So it's not surprising to learn that up to 60% of horses can be eliminated for health reasons during the competition. A team of U.S. researchers recently set out to determine which factors, at the start and in the first or second half of rides, contribute to endurance horses' elimination from competition.

"To our knowledge, this is the first study to look at a number of risk factors in a large group of horses over multiple rides to identify reasons that horses fail during competition," relayed lead author Langdon Fielding, DVM, Dipl. ACVECC, of Loomis Basin Equine Medical Center, in Loomis, Calif. "This data can help riders and veterinarians improve the completion rate and perhaps even prevent illness and injuries."

Fielding and colleagues collected rider cards (which contain detailed information about the animal) from 3,493 horses and collaborating veterinary information regarding the physical examinations during 2007 American Endurance Ride Conference sanctioned rides.

The researchers found that:

  • The overall elimination rate was 18.9% (660 of 3,493 horses);
  • The most common reasons for elimination were lameness (312/660) and metabolic problems (147/660); metabolic causes include poor heart rate recovery, colic, exhaustion, synchronous diaphragmatic flutter (thumps), and exertional rhabdomyolysis (tying-up);
  • Appaloosas, Quarter Horses, and other breeds with higher body mass index (compared to Arabians, one of the most common breeds in endurance competition) appeared to have an increased risk of elimination;
  • Not surprisingly, higher elimination rates were noted in longer rides; and
  • Abnormalities in gait at the start of the competition were not associated with elimination; however, gait abnormalities noted in the first and second halves of the competition were important and often led to elimination.

"One of the most interesting and potentially important findings in this study was that certain physical examination abnormalities such as gastrointestinal sounds prior to the start of the competition identified horses at risk for elimination," said Fielding. Other factors associated with failure during the ride included capillary refill time and overall impression by the attending veterinarian, the study noted.

"Thus, horses with specific abnormalities warrant additional attention from the veterinarians working at the ride," Fielding added.

"This study represents a step forward in the understanding of the factors that are associated with elimination from competition in endurance horses," the team concluded. "Specifically, a number of breed predilections are evident and should be considered when looking for horses to enter into endurance competition. Abnormalities of heart rate-associated variables and gastrointestinal sounds appeared to be consistently identified as risk factors for elimination throughout competition."

The study, "Risk factors for the elimination of endurance horses from competition," was published in the Aug. 15, 2011, edition of the Journal of the American Veterinary Medical Association. The abstract is available on PubMed.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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