Flame suit on.
I am convinced that too much sitting trot leads to brain damage from the pre-frontal cortex slamming against the skull. I also worry about the effects on the brain stem though I do not know enough about the brain stem to articulate what might be happening to it.
I came to this conclusion after my first foray into the COTH Forums when the Dressage section was full of people defending Rollkur. Their reactions to well-reasoned arguments were borderline abusive. I just could not understand this, yes, I know all riders have really deep seated beliefs, but the tone from hunt seat riders were no where near as vivid as from the dressage riders.
With my MS I just cannot afford more brain damage. My riding teachers know this. I can sit most trots (I have not tried with a WB with carriage horse action) but nowadays I totally refuse to sit the trot more than 6 strides, and on most days I will stop at three strides, even on horses with smooth sitting trots.
I only bring this up because I think it is important. I NEVER expect agreement about my equitation beliefs from most riders, but I was never expecting the type of disagreements to my “arguments” from these riders.
I have brain damage from my MS (and TBIs from falling off horses even when wearing riding helmets, all the sitting trot I used to do and the head on collision from a passed out drunk driver who plowed head on into my Ford Escort with a big American car.) I am not a doctor but certain behaviors remind me of myself before I learned to handle the brain damage from my MS and all of the above.
I realize most riders who sit the trot won’t listen to me, but if I can save a rider from brain damage the negative flack I get from saying this is worth it.
If I had a child who wanted to ride dressage my answer would be the same as when my oldest son, decades ago, mentioned going into football at high school and when he introduced the idea of him getting a motorcycle. I told him he had a good brain and I was NOT going to give him permission to destroy it.
Regular riding with a good riding helmet or a supposedly super secure saddle is dangerous enough to the human brain (falls.) I see no reason to add another thing that could damage my brain. This is a big part of the reason why I do not take dressage lessons, all the required sitting trot.