Honestly I thought it was a waste of money but I was desperate and wanted to try everything. I don't understand how it works, but I can tell you that my narrow back (okay, tight body) OTTB in running shoes is 100% more relaxed and warms up and runs faster and more consistently. it is better if he wears it before and after his travels. He probably has arthritis in his spine and neck from kissing (he's going to the clinic for an x-ray in a few weeks) and is in a lot of pain as a result, as well as an ill-fitting saddle. But this sheet is a *necessary* part of our efforts to treat him, along with regular bodywork. I'm newly converted and use it every day when I'm in the barn!