How do horses balance — and what we can learn from this [H&H VIP]

Balance is as complex in horses as it is in humans. Peter Green MRCVS explains why

3 mechanisms enable us to keep our balance — the sense of spatial feeling in our limbs, the vestibular apparatus in our ears and our ability to focus on the outside world using our eyes.

Sight is incredibly important for balance. Researchers in Australia wanted to find out if horses use the same mechanisms. They had previously worked out that a relaxed horse, standing perfectly still on a f at surface, has a “centre of pressure” on the ground beneath. This is the centre of weight bearing distributed between the 4 limbs.

Standing the horse on sensitive force plates revealed that, even though he appears still, he is constantly adjusting the weight on each limb by means of tiny changes in muscle activity. This imperceptible back-and-forth, side-to-side swaying allows him to keep his balance.

The researchers measured the centre of pressure in 20 relaxed, standing horses before blindfolding them and measuring it again once they had relaxed. There was consistently more movement in the blindfolded horses. Swaying was both faster and more marked side to side than back and forth.

So we know that vision is an important part of balance for horses — and that those with eye problems may not only be deficient in vision, but may also lack balance control. We must be cautious, too, when blindfolding horses for neurological examination that may have other balance problems.