This came in as a question: What is the timing of the whip in trot?
Answer: As the horse begins to pick up his hind leg on the whip side.
I have a rather long post on the use of the whip, done in the depths of winter last year here:
The timing is really easy, but takes a little practice.
You are holding your whip correctly over your thigh, the heel of your hand slightly pressing it downward.
You can feel your leg move in your hand as the whip is connected to both.
As the horse begins to step forward with the hind leg (the one on your whip side) you will feel your hip and thigh dropped a bit. Your hip, like the horse’s hip, are no longer supported. And, as the horse bends his hind leg folding it to swing through, that side drops.)
If you follow your thigh around and tic with the whip at this point the rhythm of that hind leg will be quickened. And assuming you do not let the horse sprawl in front or rush off, then the diagonal pairing will be improved.
Oddly, though you should be able to do this on both sides, it improves both hind legs as long as you make sure the horse travels straight. This is true in piaffe as well and why it is important to make sure the horse travels straight.
This is a new category–questions people are asking.
Question: Would you buy a young horse that clicks when it walks?
My assumption is that the question is joint clicking–not forging, which is when the hind foot strikes the forward heel which for whatever reason has not gotten out of the way in time–that makes a clicking sound too.
I have asked around in the past about the actual reason for joint clicking, as many of them do it. No one I have talked to seems to know exactly what causes clicking, but if new news is out, please pipe up!
Answer: given we do not know exactly what causes joint clicking–usually in the hind fetlocks–it is not a 100% deal breaker for me. But I would certainly prefer they not do it. First, though it quite possibly is ligament noise, it makes me nervous about wear and tear. Second, I associate it with stiff horses–not lame ones, but tight ones. You rarely see a loose, fluid mover with this noise. That said there is nothing wrong with working tight, strong and somewhat stiff horses–they can be good too–you just approach them differently. Also, interestingly, clicking can come and go. Some horses do it when young and then you notice that you are no longer noticing it. . .
If we are referring to forging it is typically a sign that the horse is on the forehand–retarding the flight of the front foot, allowing the back to strike it. Lots of green horses do it and as they get more balanced it goes away.