I consider Eckart Meyners to be a founding father for the future of dressage equitation. I attended one of his seat symposiums for 3 days and refer to his video tapes and his book Fit for Riding: Exercises for Riders and Vaulters frequently. I have seen instant improvement in my students when I apply the excercises he recommends. Check out this info from:
.. Equestrian Education Systems ..
Eckart Meyners
Eckart and Christina Meyners