First off I have never done a lot of endurance riding. Only ne long ride of 100 miles in two days.
Now, any endurance horse needs to learn to go on a loose rein. You cannot ride them held together for any great distance. This means that they will go with a lower head carriage = again making it safer because they are looking where they are going.
Just as a side note, this is not his normal movement, other than maybe the walk. He is usually very forward and has a large stride. I was almost wondering if he moves better when I just let him move out, but I have never had training or lessons to know when he's moving correctly or engaged. He does to great on a loose rein and, contrary to everyone "dragon" stories, he's just as behaved on a ride as he is at home. I do want to work with him lowering his head, since he's very, erm, attentive a lot of the time - head up and ears perked, looking around. He's very happy on the trails and moves out nicely, but I want to be sure he's not hallowing out his back and moving funny. Our working trot, and the pace we race at, is around 9mph and I've let him hold that pace however he pleases, which is why I'm working on basics over the winter to be sure he's moving correctly now.
Secondly some of his sore back could be from the way you rare riding. You are shoving your lower keg forward and this is making you sit on the back of the saddle every time you land from a trot rise. Constant pounding would make his back sore. Learn to keep your lower leg under you and to sit more central in the saddle.
This very well could be it, or at least contributing. I'm used to a western saddle with that leg forward - which direction should I adjust the stirrup? Obviously bring my leg back a little, but should it be longer or shorter?
Thirdly he needs to be taking a better stride. At the walk, even though his head is down, he is not using his shoulders and his back legs are only just coming to where the front feet were, they should be over stepping by at least four+ inches. He needs to open his shoulders more, taking a longer step.
At the trot he also needs to engage his back end more.
His walk is his most awkward-looking gait. He really moves at the trot - I'll attach a video of him moving out riderless on his own in the roundpen. At a walk, should I just urge him forward but keep him at a walk? And at a trot, how can I get him to take a better stride while still being collected? I don't intend to ride in rides this slow and am only doing it to work on basic stuff, so is it even important for me to collect him? (Obviously, it's a good thing simply to have a disciplined horse, but do I need to do these exercises to successfully teach him to use his body?)
If you intend to do several distance rides then get a saddle with plenty of weight bearing area. An endurance saddle , and Aussie saddle or a western, all have larger weight bearing surface than an English.
I'm saving for a Specialized saddle, which are made to fit their backs and are widely used in the endurance world. And I believe I will be much more familiar and coordinated in one lol.
Teach you horse to go on a loose rein at all paces. Learn to get out of the saddle yourself especially at a canter. Also teach him to top up with water at every stream or puddle you come across so there is no dehydration.
Have fun and good luck!
We're working on the loose rein part, but he's way better on trails than in the round pen or arena. He gets into a comfortable working trot and just goes - I love it! Of course, no one ever gets to see that side of him because they're not with me through the course of a 50-mile race (and, if they are, they're not really paying attention to my horse anyway). When a photographer or other witness does happen to pop up along the trail, so does that head! That's an Arab for you, though lol. I'm not sure what you mean to get out of the saddle - I think I already do that at a canter, but posting is still pretty foreign to me so it looks pretty bad, even to my untrained eye. As for water, he's very good about taking care of himself - always eats, drinks, and LOVES his beet pulp!