Competing unshod is an important issue for the Swedish harness industry. There is a general opinion that performance may increase significantly but it does not always work. The reason for failure may be disturbed locomotion “balance” of the horse or due to pain from the hooves. This is obviously not acceptable. We want to develop methods to predict if the horse’s hooves will cope with competition unshod. We also want to study: how performance is affected, if there are seasons and tracks that are unsuitable, what traits hooves have that cope with competition unshod, if there are genes that explain the difference between “good” and “bad” hooves and if wounds attributed to cross-firing are more or less common in horses competing unshod. This project is important not only from a short term animal welfare perspective. If we can allow competition without shoes it may benefit Swedish trotter breeding. If performance is improved breeding may indirectly promote horses with robust hooves.