Application of a Dual Force Sensor System to Characterize the Intrinsic Operation of Horse Bridles and Bits

An equine bridle tension system, with electronic force gauges in both the line of the reins and that of the cheekpiece (CP) on one side of the horse, is used to study the dynamic response of the CP tension to rein tension in the ridden horse. The objective is to quantify so-called “poll pressure.” Bits designed to give strong poll pressure using simple pulley or lever principles show a much attenuated transfer of the rein tension through the bit to the poll. The attenuation is readily understood when the equine mouth is recognized as a “floating” fulcrum degrading the otherwise required fixed pivot point of an ideal lever. Furthermore, any use of a curb chain diverts higher rein-induced CP tension to the chin rather than to the poll. Unexpectedly, however, a simple loose ring bit is found to give modest poll pressure, transferring rein tension through a pulley-like action. Finally, the curb bit of a double bridle is examined, and physical interference between the curb and bridoon mouthpieces is found. Standard, yet powerful computational signal processing of the dynamic time series tension data reveals that the poll pressure produced by the curb bit is predominantly due to tension in the bridoon reins and not the curb reins. Physical overlaying of the bridoon on the curb mouthpiece is implicated.