Join Date: Dec 2011
Location: North central Iowa
It's possible that you could've lost that posture in those 11 years. I don't know what else you do to keep fit, but not using those muscles for a while could cause them to deteriorate. Also, just getting older can cause your posture to become bad. :( Also, certain exercises like pushups, when you're a woman, can actually cause bad posture because if you have a lot of muscling in your pectoral area, it pulls your shoulders forward.
Or - perhaps your posture has not deteriorated at all. Your instructor may be having you exaggerate your posture so your two-point comes out just right. You say you are doing h/j, so I'm going to assume a lot of it comes down to the two-point. When I two-point, I have a tendency to hunch my shoulders. By overexaggerating my posture, when I forget to think about it, I have just the right posture. It's like what George Morris said about horses - overflexion is a good tool to use for a short period of time. If you overflex after you are warmed up before a class at a show, your horse will go in on the bit.
Even a slight roach in your back while jumping can be detrimental. It can cause back problems, first of all. Also, it can cause you to lose your position easier. I am not assuming that you are developing a roach, but perhaps your instructor is looking out for your well-being.
Hope this all helps.