It is great to see that there are proper studies conducted in the area of horse welfare in equestrian sports. It is high time to see dressage and head position on the agenda.
I get fed up to see the atrocious pictures of dressage horses in LDR/Rollkuer position (oh, and the showjump riders use is, too...), and many a respectable person has spoken out against it. I don't like the emotional outpourings of the dressage community, either for or against. The folks against (bless them), are particularly emotional, thereby actually hurting their own cause on occasion.
So it is with great interest and happiness that I see scientific studies that seek to find answers on these subjects. Only through meticulous data gathering and rigorous application of scientific method can we gain a measure of certainty about the things which are good and bad for our horses' mental and physical well-being.
For your reading pleasure, here is one such article:
Prevalence of Different Head-Neck Positions in Horses Shown at Dressage Competitions and Their Relation to Conflict Behaviour and Performance Marks