Drifting in one direction is a common problem for horses in all disciplines and levels. When a client raises concerns about this issue, I often look at the longissimus costarum—a small, narrow, outer back muscle adjacent to the outer edge of the large back muscle called the longissimus dorsi. The longissimus costarum extends across the lateral sides of all the ribs and connects to the thick fascia in the lower back and to the forward end that runs under the scapula (shoulder blade) and attaches to the last cervical vertebrae. When trying to find it with your fingers, it feels like a 1-inch ridge below the longissimus dorsi.
There are a few possible causes of longissimus costarum tightess, so a thorough assessment needs to be completed to determine the horse’s issue. If muscle tightness seems to be the culprit, there are three techniques that the Wilson Meagher Method of Equine Sportsmassage uses to relieve this discomfort.