In horse riding, an extended walk should find the horse reaching over and tracking as much as possible, and a collected walk should include a horse taking a shorter stride. Get tips on working walk exercises for horses with helpful advice in this video on horse training and dressage.
So, in the beginning I'd like to let my horse walk on a loose rein for about 10-15 minutes just letting him stretch, letting him have his neck, hold his neck however he would like, and just letting him warm up that way. After I've worked for about 10 minutes that way, I'll start to gather my reins a little bit and work him of a little bit of a longer frame. But not too short yet, I just want to let, put him a little bit together, get him a little bit rounder, put him on the bit a little bit but not asking too, too much yet, just letting him stride up a little bit, going more towards unextended free walk, where he's taking nice, big long strides, reaching with his shoulder, over tracking with the hind leg, that you see the hind leg reach over into, oopsies, into the footprint in the sand from the front foot and then he's nice and long in the neck, and reaching for the contact. That's moving more towards an extended walk. Extended walk, you want to see the horse reaching and over tracking as much as possible. He's a little feisty today, because it's fresh, it's windy so he's a little spooky but that's okay. You want to see a lot of activity in the walk yet also a sense of relaxation, especially at the higher level, the horses should be able to go from the highest degree of relaxation to being as feisty as possible, going into the higher degree of collection movements, piaffe and passage. So, after my extended walk, I want to gather my reins a little bit more, compress him a little bit more and shorten my walk stride, going more towards a medium collected walk. The walk, should now the stride should get a little bit shorter, the horse comes a little bit more together, I gather my reins, I want to keep him active as well, and then I go do a lot of transitions from collected walk to extended walk again, so you can see the difference where he strides out nicely, reaches for the contact. The walk is a 4 beat, so each foot is picked up in different timing, and then I gather my reins again at the end of the diagonal, picking him up, compressing him into my collected walk, through the short side, and that is how I like to work my walk exercises.
