I had Pro Power Saddles out to check Elmo's saddles earlier this week, as I try do every 6 months. The template below shows Elmo's back profile - it has changed significantly in just 6 months! He has come up through the wither almost an inch which has then caused him to loose his flat back pony shape and now resemble a horse. (You cam see how he's changed since I backed him!) This means that the width of his saddle now needs to be narrower to accommodate this.
The reason for this dramatic change is because of the thoracic sling. As mentioned in previous posts, the horses forelimb is only attached to the body via muscle - not bone. This allows the horse to roll through the trunk as it changes direction and absorb concussion over a jump. When a horse is young or weak due to being out of work the thoracic sling muscles will not be strong, this is why youngsters appear 'bum high'. As we work horses correctly, these muscles will tighten and lift the trunk which lifts the wither beyond the top of the shoulder blade giving a slightly more pronounced wither (don't panic some horses like your natives will remain flat!) This is why when a horse is excited and alert they feel like they grow - they're tensing their thoracic sling!
Over the last 6 months we have been working on more novice/ elementary moves in our lessons which require more push from behind and lift through the forehand, it's nice to see the work we have done has been working!
The problem with saddles is that they have a fixed shape tree and these vary to suit different profiles of the horses back. Some are flatter for our natives and some more curved with a higher head to suit our warmbloods etc. So it is not as simple as just making the saddle narrower to fit him, we need to consider whether the shape of the tree still fits his profile, and it doesn't! So new saddle it is!
So please make sure you have your saddles checked regularly! Not only to check they are straight and the flocking is good, but your horse may have actually changed shape and the saddle that fit like a glove last year, now may not fit at all! A saddle that doesn't fit can significantly hinder performance, cause pain and even muscle damage if left too long. I often compare it to walking in shoes that are too small - you would eventually take them off, or adapt how you're walking to make it feel comfortable. The horse - it'll either throw you off or adapt how he is moving to make it more comfortable!