what can I do

[arabianluver]

Saturday I went to my barn for a riding lesson. I've been trying to work on my leg position for jumping. To help me ,my instructor put me on a really slow horse teddy, whom you have to use your calf mucles a lot to get going. My leg was in the right place and I felt secure. I was doing great trotting without stirrups and I really felt confident in my abilities.
After the flat work our group went "out back" to do a small xcountry course. It was a total diasaster! My leg was all over the place! Also my stirrups kept slipping back to the arch of my boots , you know right where the heel is. How can I work on my leg position?

[IrisSilverMoon]

I'm not sure that putting you on a slow horse would help all that much. if you have to keep using your legs to keep him going they're liable to be moving around a lot, whether you mean for them to or not. Maybe a horse that has fine forward motion that likes you to stay in one place to jump correctly. My instructors horse is like that, if you don't keep your position he's all over the place and it's obvious you're doing something wrong, but if you hold your position steady he's a lovely jumper...:)

[ravenin]

I'm not sure I can say too much that will be amazingly helpful, but I'll say a few things...
About the stirrup falling back into your arch--I was having problems with stirrups bouncing around on my foot until I read a seemingly obvious remark: If your weight is dropped into your heel then the ball of your foot will automatically have enough weight in it to keep the stirrup in place.
It helped me to think of it as dropping my weight into my heel rather than the traditional "keep your heels down". Don't know if this will help you, but it may. This is of course related to the fact that you should not pinch or press tighter with one part of your leg than with another, which you may do without even realizing it. If you're holding on tightly with your thighs, your heels are likely to come up, your seat to head towards the cantle, and your stirrups to move around.
Also, I agree with Iris' remarks...it's hard to work on your position when you have to constantly work to keep a horse going or to slow it down. I'd mention this to your instructor if you feel you're consistently over- or underhorsed.