Join Date: Mar 2009
Location: Middle-of-Nowhere, Illinois
I don't jump any horse before the age of six, at the youngest. I'll do trot poles with 3 and 4 years olds, but nothing more strenuous than that.
Horses mature from the bottom up, so chances of you hurting their legs are much less than the risk of hurting their backs, because the back and base of the neck are the last to fully develop. Also, keep in mind that the growth plates in the legs are perpendicular to the weight they're carrying, while the plates in the back are parallel to the stress, which makes them less resilient and more prone to damage. Those bones aren't fused until around 5 1/2 years old, regardless of the horse's gender or breed. In my opinion, it's best to play it safe and stick with light work until the horse is completely done maturing.
"A musician must make music, an artist must paint, a poet must write, if he is ultimately to be at peace with himself.
What a man can be, he must be." Abraham Maslow, 1968