FACTORS LIMITING PERFORMANCE IN THE HORSE

Abstract

1495 The purpose of this seminar is to discuss the contributions of ventilation, gas exchange and its transport, and heat and fluid loss to equine performance. The horse is a large mammal with a high aerobic capacity (VO2max usually > 130 ml/kg.min-1). Contraction of the equine spleen during exercise is associated with increases in hematocrit >60% and a near doubling of the oxygen carrying capacity. This marked increase in total blood volume is associated with major adjustments in blood flow to the muscles of locomotion and ventilation. Horses also undergo marked desaturation of hemoglobin and become hypercapneic during strenuous exercise. Because of their large muscle mass and metabolic capacity, thermoregulartory factors and alterations in fluid and electrolyte balance can also play a major role in limiting the ability of horses to exercise. Due to the relative lack of information that exists regarding the physiologic responses and limitations of elite human athletes to exercise, the horse has proven to be a good model with which to study the physiology of high performance exercise. This symposium should be of considerable scientific interest and educational value to comparative exercise physiologists and students interested in factors that can limit elite athletic performance.