While he may appear to be enjoying a pick of grass as he waits his turn for a wash, on the inside his temperature is rising and every degree counts. If a horse’s body temperature rises just 3 to 4 degrees from normal, the temperatures within working muscles may be as high as 43 degrees celcius. At this temperature the proteins in the muscle begin to cook and break down. Doesn’t sound ideal does it?
Animal and exercise physiologist, Professor Michael Lindinger explains: “It only takes 17 minutes of moderate intensity exercise in hot, humid weather to raise a horse’s temperature to dangerous levels. That’s three to 10 times faster than in humans.”
Horses are more susceptible to heat stress for several reasons. Most obviously, they are larger and have a higher percentage of active muscle than humans do during exercise. Muscles produce a lot of heat when they are being used.