Plasma adrenocorticotropin, cortisol and catecholamines response to various exercises

Area of Science:

• Equine Exercise Physiology
• Endocrinology
• Sports Science

Background:

• Understanding the physiological stress response in athletic horses is crucial for optimizing training and preventing injury.
• Hormonal responses, including adrenocorticotropin (ACTH), cortisol, noradrenaline, and adrenaline, are key indicators of physiological stress during exercise.

Purpose of the Study:

• To examine the plasma hormone responses (ACTH, cortisol, noradrenaline, adrenaline) in Thoroughbred horses during incremental and relative workload exercises on a treadmill.
• To investigate the relationship between exercise intensity, duration, and hormonal responses.
• To assess the potential of these hormones in evaluating exercise-induced stress in horses.

Main Methods:

• 5 Thoroughbred horses performed incremental and relative workload exercises (80% and 105% VO2max) on a treadmill.
• Plasma concentrations of ACTH, cortisol, noradrenaline, and adrenaline were measured.
• Correlations between hormone levels, blood lactate, exercise intensity, and duration were analyzed.

Main Results:

• All measured hormone concentrations increased with exercise (P < 0.05).
• Maximal ACTH and cortisol levels were observed 5-30 min post-exercise; maximal catecholamines occurred at exhaustion.
• ACTH, noradrenaline, and adrenaline responses were more sensitive to exercise intensity than cortisol, correlating significantly with blood lactate.
• Cortisol response correlated with exercise duration.

Conclusions:

• Treadmill exercise effectively stimulates the horse's autonomic nervous system and pituitary-adrenal axis.
• Plasma hormone levels, particularly ACTH, noradrenaline, and adrenaline, can serve as valuable biomarkers for assessing exercise-induced stress in horses.
• Hormone recovery patterns differ based on exercise styles, indicating varied physiological demands.