Definition of Physiology: The science concerned with the normal vital processes of animal and vegetable organisms, especially as to how things normally function in the living organism.

Equine exercise physiology concerns itself with the cellular and chemical responses of a horses' system to exercise. We call it conditioning. Conditioning results in increased efficiency of the horses' various bodies systems so that work is performed more efficiently. Conditioning is exercise specific. The body's response to 1/4 mile fast races is different from that for a 50-mile endurance event. Let's go through and outline the changes we see in the various systems of the body with exercise. We will then take this knowledge and try to apply it to practical problems you are likely to encounter. Due to lack of space we will not detail specific training plans but will advance a number of principles to help you design or modify your program. Much of what we know is extrapolated from work in humans. However, we are beginning to see a large body of work on the exercise physiology of horses and there are some differences.

It has been shown that beginning fitness training at 18 months of age will result in a higher percentage of oxidative fibers at four years of age when compared with horses began later. There is a downside to this however: the horse's bones and joints are weaker than when he is more mature. Early aggressive training will result in arthritis. If you must train at this age, I strongly recommend ponying on the trails at slow to moderate speeds for short durations.