The role of cortisol hormone in equine exercise physiology

In the following review article the authors illustrate the complexity of the hormone cortisol, and discuss the relevance of the hormone in exercise physiology, several conditions may induce a cortisol release, the effect of this hormone is diverse throughout the body. Researchers investigating the cortisol response to different stressors, reach often contradictory conclusions. Exercise is a unique and complex stress factor, which means physical and psychical challenge at the same time. Anticipatory stress response is a well-known phenomenon in sport psychology, which means increased serum cortisol level before exercise, even without any physical strain. Therefore the correlation between exercise and cortisol production remained to be unclear so far. Some researchers have found cortisol relevant for measuring the workload, while others have used the cortisol measurements for assessing the current fitness level of the horse. There are also numerous studies that failed to prove the usefulness of cortisol measurements in equine exercise physiology because the production of the hormone is influenced by several confounding external and internal factors. The exact trigger for the cortisol increase during exercise is also questionable. Results of the comparison of cortisol responses between different types of exercises suggested that the duration of the physical activity is a more relevant trigger than the intensity of the exercise. Although opposite opinion can also be found in scientific literature. The aim of the authors is to overview the scientific evidence in this topic available today. In the article the possible causes of the existing contradictions are high-lighted, and a practical approach for the use of cortisol measurements is provided.