Distanceriding.org - Full Article
Gayle Ecker, Equine Exercise Physiology
These suggestions are a combination of the results of my research (along with Mike Lindinger) as well as the result of many discussions with riders, veterinarians and pit crew people.
The recent thread on heat stress in endurance horses generated a great deal of very good discussion about optimal management of the endurance horse. Concerns have been raised about the number of horses at the PAC that needed treatment.
Electrolyte supplementation, while a VERY important part of the equation, does NOT address the heat build up that occurs with exercise. The major route of heat dissipation is through the evaporation of sweat. Note that we said the evaporation of sweat. Sweat that runs off the horse or sits on the skin without drying quickly will not contribute greatly to the heat dissipation. A high humidity level will compromise the evaporation of sweat, even if the weather is cooler. During our research, we have documented significant losses of water and electrolytes even in cool weather because the humidity level is high. The horse still generates large amounts of heat, but dissipation is compromised due to the high humidity. Water and electrolyte losses can be high with high humidity even if the temperature is around 21 d C or 72 d F.
We are fighting physics. The horse does not have as much surface area to dissipate the heat as does the human. Nor can we force the horse to drink as much as it needs to replace the water losses. Of all the horses we have included in our research studies, NONE had enough water to replace the losses. Most never came more than ½ to 2/3 of the water loss. While this may not have put the horse in a position where vet treatment was necessary, these losses were certainly at a level where circulation and cell function would be affected. This would definitely impact continued performance. For the horse that is working within its capacity, this may not have a noticeable effect, but the horse that is being pushed a little harder may have greater problems with the added stress...
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