What’s the Best Cool-Down After Exercise?

By Adam Marcus

The key to cooling down an overheated horse is a long cold shower.

Researchers in Japan compared 5 methods for cooling horses after a workout in nearly 90° heat and high humidity—a potentially perilous combination for equids. The animals were exercised until their body temperature, as measured at the pulmonary artery, had climbed to 42° C (107.6° F).

Using hot walking as the standard, they looked at other cool-down methods, including walking past electric fans, walking with the periodic administration of cold water (10° C; 50° F)—with and without scraping—and a long shower in 26° C water (78.8° F).

They found the cold shower was the most effective method and hot walking was the least efficient method of bringing the animals’ core temperature down to below 39° C (102.2° F). The use of fans, and occasionally water, were modestly faster, but didn’t differ significantly from each other, according to the researchers.

Andrew Dart, BVSc, PhD, DACVS, DECVS, the director of the Research and Clinical Training Unit at the University of Sydney in Australia—who was not involved in the study–said it had important implications for managing horses with Exertional Heat Illness (EHI) and other heat-related symptoms.

“The importance of this syndrome is that it is really not in the mainstream equine literature and is poorly understood, studied, documented and is a significant welfare issue in thoroughbred racing in countries where the climate is hot and/or humid,” Dr. Dart told Modern Equine Vet.

EHI differs from heat exhaustion in key ways, Dr. Dart said. “In the heat exhaustion syndromes in eventing and endurance horses, horses perform at submaximal exercise over distance, therefore in an aerobic capacity with dehydration and electrolyte imbalance becoming the driving factors leading to poor circulation,” he said. “In EHI, horses exercise in a largely anaerobic capacity: at maximal exercise intensity, over short distance. The rapid production of energy associated with the intensity of work results in a rapid increase in body temperature that overwhelms the thermoregulatory mechanisms.”

Horses with EHI may quickly develop clinical signs of heat illness—slow recovery, excessive sweating, irritability and uncooperative behavior—that progress to more serious issues like ataxia, falling,

coma and death. “In many cases the clinical signs are nonspecific and the veterinary teams do not institute the early, aggressive and rapid treatment that needs to be instituted,” Dr. Dart said.

“While there are similarities and overlaps in the pathophysiology of EHI and heat exhaustion syndromes the treatment priorities are quite different,” he added. “In EHI, rapid cooling is the key once clinical signs are beginning to present. Of course, better recognition and information [are necessary] around the predisposing environmental conditions. Preventing and managing conditions are vital and in most jurisdictions needs to be based on facts but is currently highly varied, non-specific and ill-informed.”

Although showering in the new study appears effective, Dr. Dart noted that it demands large volumes of water. As a result, if it were to be used at events, for example, several stations would be necessary, and some animals might require sedation. “Of course, this is a study and the effectiveness under real conditions would need to be established and may need refinement. However, I do not see any downside of moving this forward,” he said. “This is a nice study, and one that is really about ensuring the importance of EHI as a welfare issue for the racing industry world-wide and how simple and effective prevention could be.”

For more information:

Takahashi Y, et al. A Comparison of Five Cooling Methods in Hot and Humid Environments in Thoroughbred Horses. J Equine Vet Sci. 2020 Aug;91:103130. doi: 10.1016/j.jevs.2020.103130. Epub 2020 May 22. https://pubmed.ncbi.nlm.nih.gov/32684268/