More than sixty percent of the total body weight of a horse is formed by skeletal muscles. An enormous mass that immediately indicates the importance.

During exercise, many physiological processes in the body change. In just a few seconds, heart rate, ventilation and oxygen uptake increase. Regional and local changes are also taking place. The blood flow to active muscle groups, the lungs heart increases, while that to inactive muscle groups and organs (eg the intestines) decreases. This makes that the body is challenged during exercise. With increasing intensity of the effort, the load will be tolerated up to a certain limit. Where this limit lies and how this maximum limit is determined, is different for each horse.