The Jockey as a tail: How can a jockey influence horse performance?

Historical horse racing records show that a dramatic improvement in horse racing times (5-7%) was directly correlated with the adoption of the “Martini glass” Jockey posture, and this crouched posture is thought to decouple movements of the horse and rider, as demonstrated by kinematic observations [6]. That is, the jockey uses their legs to move relative to the horse in such as manner as to cancel the horse’s motion, such that the jockey’s mass moves little in the inertial (world) frame, such that the horse must supply a constant force equal to jockey weight, but not additional forces to overcome jockey inertia. This paper proposes three topics for workshop discussion, that stem from this work. The first is: what modeling and analytical approaches, mathematical or robotic in the former case, could best give insight into this phenomenon and make new, testable predictions? Recent such work considering elastically coupled loads [1] has given insight into optimal coupling mechanics and the benefits of elastic coupling. The second relates to the open question of whether the jockey can employ another, different movement relative to the horse that improves maximum speed. We provide a simple conceptual outline of a phasing of jockey fore-aft oscillation relative to the horse that could improve stride length, and potentially reduce required horse leg work, relative to a jockey that is fixed with respect to the horse.