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AUGUST 2006 • VOLUME 12 • © Copyright HORSES For LIFE™ Publications
A NOTE ON THE HEAD BOB IN THE GALLOPING HORSE AT LIBERTY AND THE HARMFUL EFFECT OF THE BIT ON THE HEAD BOB1 W. Robert Cook PhD., FRCVS
Professor of Surgery Emeritus, School of Veterinary Medicine, Tufts University The natural swing of the head and neck pendulum in a galloping horse is known as the head bob. The degree of head bob, as with all other characteristics, will vary from horse to horse. But, in general, it seems reasonable to assume that the more the better, as this is a mechanism that enables a galloping horse to conserve energy spent on locomotion and respiration.
Figure 1: Showing how, in a horse that is galloping at liberty, the head bob constitutes an energy-saving mechanism. One complete stride at the gallop is here represented by examples from its three major components; fore leg weight bearing, suspension phase, and hind leg weight bearing. The first and last phases have been chosen as representing those moments when the head bob is at its lowest and highest, respectively. As a horse at the gallop breathes in time with its legs and takes one breath for every stride, the phases of the gallop synchronize with the phases of respiration. See the text for an explanation of the numbered items. The cascade of events can be described in eleven stages.
1. The forelegs become weight bearing and a momentary deceleration occurs
2. The force of gravity results in a downward movement of the head and neck
3. This stretches the strong elastic rope (the ligamentum nuchae) that runs from the back of the skull to the withers and forms the top line of the neck.
4. The downward swing of the head/neck pendulum has a cantilever effect on the rest of the spine which, unlike the neck, is rather rigid. The result is that the tail end of the spine is raised.
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