The coach should be telling you how to ride a hh, get the horse up and open, and keep it active. I take it that you mean 'strung out'? Which would indicate that the reins are too long. (Is that your pix on the top left? Of this horse?) A horse should show a significant change in its (neck) muscling in only a couple of months, and a much 'bulked' top line in 6. What exercises are you doing?

He's still quite young, if he's coming 4. Regardless, the only way to build the topline is for the horse to be through his back and start working more off of his hind end. I agree that your trainer should be able to tell you how to get *this* horse engaged.

If the horse is 'strung out' then some of the following things are happening: it is too lowered/too long/too closed/cannot take a proper hh. The horse has to be ridden up and open. Yes, hills develop strength and let the horse use its body more entirely, but caveletti/small fences can do the same thing. Figures which encourage lateral flexibility do also (circles/half circles/broken lines/etc). If the horse is up and open it will be free(r) to let the hind legs step through and therefore take longer strides actively, and that is what develops the top line (not longer or lower). We only have to look at the 'tubular necks' of many fei horses today to see that. I have ever seen a horse which does not not only track up but over track when run free, so we have to look at how our riding technique causes that to be lost/taken from the horses. Even in collection where energy goes into amplitude there should be clear lifting and placing of the hind leg, and freedom of the shoulder. All horses should start to show a kind of stallion top line (both on the crest and in the width out of the shoulders tapering toward the poll) within 3 months, and continue laying down more and more both on the neck and over the quarters for the rest of their lives. If not, something is missing.

Don't worry about a 'frame' (which might be too low/closed or being held at the vertical). Such young horse should be up (mouth about the level of the point of the hip) and very open (perhaps 45 degrees in front of vertical and certainly NOT routinely at the vertical), and active. Long straight lines, nice use of corners, big circles, active after transitions.

But we need more info imho.

What exercises is she showing you? In what bearing?

HH/demi arrets usually come before application of activity on a horse which is too low imho. Shoulder fore/in, renvers, travers are engaging/straightneing/suppling, but LY is really only suppling. The purpose for quick transitions (esp down) on a young tb (unless he is dull) which is too lowered or closed is?