Scientific reasons in support of using a bitless Bridle according to Dr. Cook:
In a study of behaviour, a survey was carried out of 440 reports from riders who switched from bitted to bitless bridle. It compared the invasive and painful bitted bridle to the non-invasive and painless bitless bridle. The survey showed the bit to cause at least 50 behavioural problems. The most frequent were fear, rebellion, a flight response, and facial neuralgia (headshaking). These and other problems were associated mainly with oral pain, yet weren’t limited to the oral cavity. They included a cascade of systemic effects. They mainly concerned the nervous system and caused adverse behavioural responses (58%). Musculoskeletal system effects impeded locomotion (26 %), while respiratory system effects resulted in breathing difficulties or dyspnea (16%).
Furthermore, the fact that the method has been in use for a very long time doesn’t assure its fit for its purpose. The main disadvantage of the bitted bridle is that only a very skilled rider with an unshakably independent seat can use it without major discomfort for the horse. In the hands of an average rider it causes pain, while if used by a beginner it means torture for the animal.
‘Good’ hands depend on having very little or no pressure on the bit. As the horse’s mouth is one of the most sensitive parts of its anatomy, even slight pressure can cause considerable pain. The horse exhibits this pain through the four F’s: fright, flight, fight or freeze. Besides it being the main cause of accidents to both horse and rider, the bit can obstruct breathing and impede correct movement. The bit stimulates the gastro-intestinal function, which is physiologically opposite to fast breathing. Therefore, the horse receives feeding and work signals at the same time, which is problematic since they are mutually exclusive activities. It has been concluded that using the bit is detrimental to the health and safety of both horse and rider, as well as an impediment to performance.
An important advantage of using a bitless bridle can be painless, stress-free, and relaxed communication between horse and rider. Painless communication inevitably leads to more effective control. The bitless bridle aids communication by distributing pressure more evenly over the horse’s head, which makes the pressure milder and thus more acceptable. It enables a more humane, non-invasive, and natural approach suitable for early and advanced schooling alike.
Source: Patophysiology of bit control in the horse, W.Robert Cook, FRCVS, Ph.D.