About 2 weeks ago, a friend and I bought two off the track thoroughbreds. The trainer I am working with says that I should not jump my horse a lot because his stifles and other muscles need built up so I can have a good base and he can become more solid before jumping. However, my friend has been jumping her horse every day (not exaggerating) and she has been jumping him over 2 foot verticals. Is this bad for him since he has no muscle tone, lose stifles, and absolutely no basic training? Is it better to teach them the basics of flat work before jumping?