Physics of Equine Locomotion

Canter

The canter, referred to as a lope in western disciplines, is a three-beat gait. Either front leg can initiate the stride; if it is the right leg, it is a right lead canter, and if it is the left leg, it's a left lead canter. There is an airborne phase after the leading forelimb has left the ground. There is a larger side to side rocking in this gait than the next one, the gallop1. At the canter, the head-neck junction rotates counter clockwise and, following Newton's Third Law, the trunk-neck junction has an equal and opposite clockwise motion, which aids the hind limbs in lowering to make contact with the ground2. (For the definition of Newton's Third Law, see the section in 'Anatomy' called 'Knees and Toes'). In the canter and gallop, which are asymmetrical gaits, the legs don't all experience the same degree of force. The front end carries more mass and generates greater forces (F=ma). Additionally, the time of contact between the hoof and ground varies between legs in these gaits. The leading forelimb must counteract the most force as is the main landing leg and also acts to push the horse foreword as well.


In this video, a gaited horse is seen cantering (for more information on what gaited means, see the section on 'amble'); canters are not significantly different between gaited and non-gaited breeds. This horse is on a left lead; the leading foreleg is the one closest to the camera. Pay attention to the short period where no legs of the horse are in contact with the ground after the leading leg is lifted.



Video source:https://www.youtube.com/watch?v=mUiLh65Y6G8

Gallop

When a canter becomes sufficiently fast, it will develop into a gallop. This is a four-beat gait where the strides have become so long that the diagonal limbs that were landing together are now dissociated and there is a second airborne phase in between. Motion from accelerating the head forward starts the airborne phase and can lead to lengthened stride2.


The horse in the video is galloping. The horse is leading with the right foreleg (the one towards the camera). Notice how unlike in the canter video, the non-leading foreleg an the diagonal hindleg do not land at the same time. The head is lifted just before the takeoff of the leading leg (this is most noticeable at the beginning of the video); the torque of the head and neck is used to lift the front end and lower the back end.




Video Source:https://www.youtube.com/watch?v=9PK1NdQAGRQ