Wow this forum must be one of the best kept secrets on the net! Great advise. Now I have a question as well.
How do you teach your horse "consistant rhytem"?
My horse is an 8 y.o. wb/tbx and has done PC and ARC level 2 and 3. Our new instructor wants to bring us back to "basics" and says my horse has a problem with "inconsistant rhythem".
Would be grateful for any tips!

Lets define "rhythm":
Rhythm is the regularity and repetition of the footfall in each gait. The tact.
(e.g. walk 4 beats, trot 2 beats, canter 3 beats)

Rhythm and relaxation go hand in hand and both are essential when training a horse. Only if the horse is physically and mentally relaxed he will be able to move confidently, in balance and without tension.

"To help regulate the rhythm is the most important duty of a rider on a young horse" (I think Dr. Klimke said this).
But how can you "teach" rhythm?
Well, I wouldn't say that you "teach" rhythm, because a horse already has a natural rhythm. I think the answer to finding and maintaining this "consistancy" (or regularity) that your instructor refers to, requires you to be aware of the footfall and of your very own balance while being in motion WITH your horse.
In trot for example the footfall should be 1-2-1-2-1-2 (not 1....2-1-2-1...2 or whatever).
If you are in balance WITH the horse, he will carry you with regular strides and the weight (his and yours)will be distributed more in a way it is natural for a horse. (Horses do naturally carry more weight on the forehand, HOWEVER, with the additional weight of the rider, even more weight is on the forhand. Progressive training restores the natural weight distribution by making the horse more athletic. He will become stronger and more supple so he can step further under his body with his hindlegs and therefore taking some of the extra weight on his haunches and off the forehand.)
So, your first step to consistant rhythm would be to conciously stay in balance with the horse and not interfere with his natural rhythm. If for some reason this regularity is upset, it is your job to regain the balance and your horse's attention asap and therefore to help him to rebalance under you - physically and mentally, going back to the 1-2-1-2-1-2.....
This is the hard part as it requires you to be in control of your body and mind, resisting your "instincts" to "hold on" or pull on something or disturb the horse's balance by tilting your body. You must learn to rebalance yourself, staying over the horse's point of gravity. If you stay in balance with your horse's point of balance, no matter what happens, then you can help regulate your horse's rhythm by "holding him" when needed or encouraging him with what you've got: Your independant balance, your aids - your centre, your seat.....
Once the horse and you have developed the confidence in the regularity and the freedom of movement that comes with it, you can start influencing the length of the stride.... but that's another story.....