If Horses Could Speak, Gerd Heuschmann

Gerd Heuschmann has a book called Tug of War that explains how riding and equipment affects the horse.

See the previous post here:

http://iceryder.blogspot.com/2008/10/gerd-heuschmann.html

Now, he has a DVD coming out, and here is a sample:

http://www.stimmen-der-pferde.com/index/Trailer?STLWEB=en