A tongue-tie is a piece of equipment used by horseback riders to prevent the horse from getting his tongue over the bit

Bit (horse)

A bit is a type of horse tack used in equestrian activities, usually made of metal or a synthetic material, and is placed in the mouth of a horse or other equid and assists a rider in communicating with the animal. It rests on the bars of the mouth in an interdental region where there are no teeth...

, which would make the animal very difficult to control. It is usually a strip of cloth or rubber, passed through the mouth and tied below the chin.

Tongue ties are illegal in most competitive events. The device is controversial in some circles where its use considered abusive. However, due to the life or death safety and control issues inherent in certain sports, such as horse racing

Horse racing

Horse racing is an equestrian sport that has a long history. Archaeological records indicate that horse racing occurred in ancient Babylon, Syria, and Egypt. Both chariot and mounted horse racing were events in the ancient Greek Olympics by 648 BC...

, it is considered by some to be a necessary tool for some animals used in extreme horse sports. What these sports don't realize, the tool becomes necessary due to the horses inablity to "accept" the bit, whether it be that they were broken in rather abruptly, or the jockey / track workers heavy handedness. Horse Psychologists would argue that the need of a tongue tie is indication of a deeper underlying issue, that a tongue tie itself, only bandaids - does not solve.

Research has shown that the tongue-tie does not restrict the animal's breathing. However, research has also shown that the tongue-tie does not provide a respiratory benefit in healthy animals (as some trainers believe it prevents the horse's tongue from coming up, and therefore allows for free air intake). Other studies have shown that it does help prevent dorsal displacement of the soft palate, but success rate is low.