There are a few potential reasons why your horse may move or back up when you are trying to get on. The first and most common reason for your horse doing this is simply that they may not have been taught to stand still in this situation. Just as dogs can be trained to ‘stay,’ horses can be taught to stand when you are mounting from the ground. Your horse backing up when you mount may also be a sign of a ‘cold back.’ A cold back refers to a scenario where your horse has discomfort in the muscles which run along their backs, often caused by an ill-fitting saddle. A cold back could also simply be just that; your horse’s muscles are cold and stiff and need time to warm up. In this instance, your horse may stiffen and brace its muscles for your mount by moving backward.