Most of the sports we do can be enhanced by a little physical training. Of course, most organized sports encourage strength and cardio work on top of playing the actual game. Also individual sports like skiing, rock climbing and cycling all benefit from some extra-curricular training. It seems logical that horseback riding, requiring strength and endurance to hold on, stay balanced, change direction etc would benefit from some training. Pilates may not be for everyone, but it is interesting to note what muscle groups they suggest you target and it does seem to be a good fit for some equestrians.
Check out this link to an About.com article describing an equine Pilates workshop in Colorado. I found it first in Kathrine’s Horse Blog. The workshop was put on by Pam Harrington, Pilates instructor and Patty LeBlanc owner of Cappaleigh Farm.