just gonna add my penny's worth....
What feels 'long and low' to a rider is not necessarily unbalanced and on the forehand.
My mare is western trained so is quite happy to toddle round in a relatively long low outline. At the same time she is engaged and tracking up. This is not necessarily at speed - more at something approaching a western jog.
By allowing the horse to adopt a slightly lower head set, and lengthen along the back - you are also freeing them up to step slightly more under and through.
Try it yourself on all fours. If you have your head up, and try and bring a 'back leg' through, and then try it with your head level (not down) and see the difference..... (but if you round your back like a cat does and try again, i.e. over-round/deep style, all sorts of weird stuff starts to happen - trying this will give you a feel for the extremes to avoid as well as the point you are aiming for !).
There has been previous threads about excessive use of "Long and Low" - but a lot seems to be in how you define it - i.e. not too "deep". You want just enough that the horse is using his topline, without over stretching joints and ligaments and ending up unbalanced.
I think the other important thing here (as has already been said) is that working long and low is a part of the whole, not the whole itself. e.g. part of warm up and cool down, part of helping a horse understand how to lift his back etc.
and to try and address some of the original questions....
- try to make sure that the work is active, especially behind - but not rushed. If the horse is active but not too forward, and in self-carriage, then it becomes more difficult/unlikely for them to be on the forehand. It may take some time for them to learn how to do this, so start with short stretches of "LandL".
It can actually be a really good exercise to ask them to maintain long and low through a transition, as well as helping them maintain the long and low - so transitions and half halts are good. aim to keep them soft and quiet, without 'creeping' up the rein.
I found that starting to ask while doing lots of turns and circles helped keep my mare loose and supple, whilst keeping the speed sensible. Make a snake trail !
I also find long and low leg yield is a really good rider exercise, as asking for sideways movement without getting (a) increase in speed and (b) without using the reins means you really have to be tuned in to your horse and yourself. It is also useful to keep the horse thinking, using itself, and not rushing off.
[Our first attempts at jog were lacking engagement so had hind feet dragging. But now we're getting the hang of it. It was easier to get at first from trot, slowing down, rather than from walk. But now we're getting better at walk-jog.]
