Just because a saddle fits a horse that’s standing still doesn’t mean it will still fit when the horse is moving, because saddle fitting for the horse in motion has to take into account how the horse’s back changes. I came across an interesting post on Facebook by Erica Allen, a certified independent saddle fitter in Ontario. I learned a lot from this post. I hope you will, too.
*** Why Tree Shapes Matter….For Your Horse ***

Horses come in all shapes and sizes & are 3 dimensional creatures. Saddle trees also come in all shapes and sizes and are also 3 dimensional objects. Most people seem so fixated on the width of a saddle/tree, which is unfortunately only one very small part of saddle fit as a whole.
Here is an exceptionally interesting and obvious example of just WHY tree shape matters to your horse. Make some tea, pour some wine & have a seat, this is likely to be a bit long.
Horse: 5y/o KWPN gelding owned since a weanling & all training done by his owner. Horse has been doing very light work a couple days a week in “Saddle A” since he was 3.5, with frequent bouts time off as dictated by growth. The rider has been struggling to get him soft and not inverting, especially in the canter for some time now. <— Hence why I was called.
Photo # 1: his back shape standing still
Photo # 2: his back shape while trotting
I hope everyone can appreciate that these 2 back shapes are entirely different! This lovely boys wither basically disappears when he starts to move. As a fitter, it would be completely useless to everyone involved if I fit a saddle to this horses “standing shape”. No one cares if a saddle fits in the hall way. Well…….ok, maybe that’s wrong……..if there is someone on this earth who just likes to saddle their horse and stare at how pretty they are in the hall way – then fitting the saddle statically would be useful to them. Hahahaha For most people, we actually own a saddle and a horse so that we can ride. So a fitter, it is my duty to ensure the saddle fits while the horse is in motion – so I must fit the flatter profile back of this lovely gelding.
Photo #3, 4: Saddle A on this horses back.
This saddle, while standing still, really doesn’t look too bad on this horse right?? If you run your hands under it everywhere there is pretty even contact. Essentially it would technically pass the “fit requirements” based on look and feel for the majority of riders and even for some professionals & fitters.
While I don’t have video of this: I can promise you, that while in motion, even with a rider in the saddle, the back of it lifts up, putting the balance of the seat too far forward and the back actually bounces on the horses back, especially in each canter stride. See that drop from the top of the pommel down to the base of the seat? Yeah the entire area is now baring the majority of the weight of the saddle & rider, and actually pushing this boys back DOWN at the base of the withers (lowest point of his back).
Now please go back and review photo # 2 (horse trotting without tack). Can you see the odd muscling over his back that is EXACTLY where the saddle sits?? Yes, that is from this saddle that isn’t allowing those muscles to fire or function properly. This is not from a lack of topline, feed deficiency, or lack of correct work. This is from a saddle IMPEDING the horse from being able to move properly under saddle. The horse cannot lift his back, therefore cannot be soft for his rider, and yup – the canter suffers the most as that gait requires to most back movement.
So what fits this horse?
Photo # 5, 6: Saddle B on this horses back
Notice the saddle looks pommel high? I totally agree it does! It also looks like the rider would be seated in the back seat if she rode in that. Notice the saddle doesn’t have a deep seat? Nope it doesn’t. Notice it doesn’t have a very high pommel? It looks pretty darn totten flat! I totally agree! But……refer back to photo # 2 of the horse trotting without tack on; what does his back look like?? Yup, you got it……Flat. So, the tree shape front to back MUST match that of the horse. This tree is also a full tree size wider than Saddle A – and yes it’s the same brand, and they size their trees evenly between makes, so this is a fair representation from a width stand point. Some may ask “well what about the balance point being so far back in the seat?? The rider would feel like she’s driving a car from the back seat & will be in a chair seat!” It absolutely does appear that way. But when that horse moves, the back comes up so much, that the seat levels out and the rider is perfectly balanced right where she needs to be.
Photo # 7: Rider aboard saddle B
You can see in this last photo that despite the seat being enormously way too big for this tiny bummed rider, she is perfectly seated right where she should be in the saddle, and it no longer appears pommel high/cantle low. Horse was immediately soft and the canter transition was improved and the owner said the canter hasn’t been that good in a long while – no more inverting – Yay!!!
Now this owner was quite the smart cookie 2 years ago when she bought Saddle A custom for a 3y/o. Sounds scary right? Look how much he’s changed shape!! His owner went with a company who accepts trade ins for just such an occasion! So what will happen? Saddle B will be ordered (in a smaller seat size for sure!) Saddle A will be given back to the company (to be resold) and the trade in value of Saddle A, will come directly off the invoice for Saddle B. Sounds amazing right? I won’t lie, it kinda is. Now most Saddle companies don’t offer this exact same thing, they may offer a variance of it, but it doesn’t usually work this smoothly at all. So in that regard, this horse/owner pairing totally hit the jack pot!! They will be well on their way to bigger and better things very soon!
So, hopefully this helps everyone see, that tree shape……..MATTERS………a lot!