Thermoregulatory adaptations associated with training and heat acclimation

Area of Science:

• Equine Physiology
• Exercise Science
• Thermoregulation

Background:

• Exercise generates significant metabolic heat in horses, necessitating effective thermoregulation to prevent dangerous hyperthermia.
• Horses possess efficient heat dissipation, but can be overwhelmed by intense exercise, hot/humid conditions, or impaired thermoregulatory mechanisms (e.g., dehydration, anhidrosis).

Purpose of the Study:

• To investigate the physiological adaptations conferring improved thermoregulatory ability in horses through exercise training and heat acclimation.
• To determine the effectiveness of different training regimens in mitigating hyperthermia risk during exercise in hot environments.

Main Methods:

• The study reviews existing research on equine thermoregulation during exercise.
• It analyzes the physiological adaptations resulting from exercise training in cool conditions and heat acclimation through repeated exposure and exercise in hot environments.

Main Results:

• Both exercise training and heat acclimation lead to physiological adaptations, including expanded plasma volume, improved cardiovascular stability, and enhanced evaporative heat loss via altered sweating responses.
• The magnitude of these adaptations is proportional to the thermal load; heat acclimation induces greater changes than training in cool conditions.
• These adaptations collectively attenuate core body temperature rise during exercise.

Conclusions:

• A 2-3 month exercise training program tailored to the athletic demand is essential for horses competing in hot conditions.
• While cool-environment training aids exercise response in heat, a 2-week period of moderate exercise in hot conditions optimizes thermoregulation and performance.
• Heat acclimation does not eliminate the need for vigilant monitoring, especially in hot, humid conditions where sweat evaporation limitations can still lead to severe hyperthermia.