I'm just getting back into riding after a hiatus of a year or so. I've found a really great trainer and have made a lot of progress the last couple of weeks. One thing I'm finding a bit difficult at the moment are transitions from canter to trot. For some reason I don't have trouble doing this over simple courses, but when working exclusively on the flat I feel "discombobulated". Basically when I go back to a trot my legs feel a bit loose and my upper body isn't entirely still. It takes a couple of strides at the trot in order to regroup.
In contrast, the upper transitions are fine and so are downward transitions from the trot.
What suggestions would people have for exercises to correct this?
Go through this checklist for all your downward transitions.
Leg... Seat... Reins (in that order)
Leg: Place your leg on your horses side to maintain momentum and encourage impulsion from his hindquarters. And as always Heels down!
Seat: Your seat should sit into the saddle deep therefor signaling to the horse that something is going to change. Should you seat be out of the saddle and the horse proceed to downward transition then you will inevitably fall forward with the momentum of the horse slowing down. Remember always prepare yourself before you ask your horse to perform.
Reins: Now obviously those reins are the final signal to the horse to slow down. Careful though to use light pressure only and not yank. If the rein pressure is too abrupt then the trot will slow to nothing then you'll struggle to get the rhythm of your post.
Leg... Seat... Reins
Hope that helps!
If you will half halt before your downward transition, it will be smoother and easier to ride well. Sit for a step or two before you pick up the post when going from canter to a trot. Don't use just hand/rein, as the will fall onto their forehand, and you'll get a lousy, unbalanced transition. Leg is important. Having a strong core will help immensely with your riding, especially downward transitions. Do some crunches and back exercises. Look up "Legendary abs- 6 min abs" for some quick, very effective exercises.
It sounds like you are "dialing in" the canter-trot transition rather than actively riding it.
Can you make the canter bouncier and shorter strided with the horse rocking back onto his butt when you ride? If you can do this by pushing the horse forward and up to the bit (push when the horse's front end comes up in the canter stride) you can progressively in several strides rock him back more and more and more until he says "I gotta trot!", and in the next upswing you put your leg on, support with the reins and push him forward into the trot. It's probably going to be a big trot that will need to be steadied and collected a bit.
The first time you try it may take a lot of canter strides to get to the "gotta trot" moment, or you'll miss it and the horse will trot, or you won't quite get there because you're trying too hard to keep cantering, or your forward to trot timing/feel will be off. One of the major keys is to do the forward and up to the bit pushes and the forward to trot push when the horse's front end is coming up. Think of trying to get his shoulders up higher, then think of pushing the shoulders forward in the up position into the trot. If you go forward to trot on the down the horse will sort of splat onto his forehand into a rough trot.
Once you have the timing and feel worked out you can progress to doing the transition with fewer bouncy canter strides, and have a better trot coming out. The horse will learn to be better balanced through the transition as well.