Understanding how high your horse can lift his/her trunk and back gives us important perspective. We can estimate overall condition and state of training if you send us a photograph of this movement as part of your Free Saddle Fit Evaluation. Then, we can help you set up your equipment to accommodate the shape your hrose becomes when moving.
Here's an explanation of how to cause your horse to contract abdominal muscles and simulate the lift that occurs when he/she is in natural motion. We call this the "belly tickle". You'll need a friend with a camera to help you get this shot.