Experience and instinct tell us to condition older horses carefully, keeping a close eye on how they handle their workouts. A team of researchers at Rutgers University confirmed these instincts when they examined senior horses’ propensity for developing hyperthermia, or elevated body temperature, when exercising.

Led by Kenneth McKeever, PhD, FACSM (fellow of the American College of Sports Medicine), a professor in the Department of Animal Science, a team of researchers examined older horse’s propensity for developing hyperthermia, or elevated body temperature, when exercising.

In previous studies scientists have examined horses’ ability to thermoregulate during physical exertion, but they had not evaluated the older horse population specifically. In the current study researchers evaluated relationship between physical exertion, thermoregulation, and plasma volume in six younger (7 to 8 years old) and five older (mid-20s) unfit Standardbred mares working on a treadmill.

The horses exercised until their core body temperatures reached 40°C (104°F, the normal temperature for an average adult horse is 99-101°F or about 37.2-38.3°C). The investigators monitored the animals’ core, skin, and rectal temperatures, as well as heart rate, every minute during and immediately post-exercise. They also collected blood samples from the horses before their body temperatures reached 40°C, at 40°C, and every five minutes until 10 minutes post-exercise, later analyzing the samples for packed cell volume, lactate, and plasma protein. Sweat loss was also estimated using body weight as a reference