When we talk about bit fit, much of the conversation focuses on the physical dimensions of the bit itself — its width, its thickness, its shape. But understanding how bits work requires us to go a step further and consider something perhaps even more fundamental: where pressure is applied, and what effect that pressure has on the horse's body, mind, and way of going.

Different bits create pressure in different places, and each pressure point has its own characteristics, its own sensitivities, and its own influence on how the horse responds to the rider's aids. Understanding bit pressure is not about finding ways to create more control — it is about understanding the horse's mouth and body well enough to select and use equipment that communicates clearly, comfortably, and sympathetically.

Tongue pressure

The tongue is the largest structure in the horse's mouth and the pressure point that the majority of bits act upon most directly. It is a large, muscular organ that fills most of the available space in the mouth cavity, and because it sits directly beneath the bit, it inevitably receives a significant proportion of whatever pressure is applied through the reins.

Tongue pressure, applied correctly and in appropriate measure, can be an effective and relatively gentle means of communication. The tongue is well supplied with nerve endings and highly sensitive, meaning that even light rein contact can be felt clearly and distinctly. For a horse that is correctly trained and working in self-carriage, gentle tongue pressure provides a clear, consistent signal that the horse can respond to with softness and relaxation.

However, the tongue is also vulnerable to excessive or prolonged pressure. When too much pressure is applied — whether through the design of the bit, the thickness of the mouthpiece relative to the available space, or the heaviness of the rider's hands — the horse will instinctively attempt to relieve it. 

The most common evasions include putting the tongue over the bit, drawing it back into the throat, pushing it to one side, and opening the mouth to try to shift the bit's position. All of these are the horse's rational response to discomfort, and all are frequently misidentified as training problems when they are in fact equipment issues.

It is also worth understanding that the tongue and the jaw are intimately connected in terms of tension and relaxation. A horse that is tense and braced through the tongue will almost always be tense and braced through the jaw as well, and that tension will travel upward through the poll and down through the entire topline. Conversely, a horse that is soft and relaxed in the mouth — gently mouthing the bit, producing a small amount of saliva, chewing softly — is showing that their tongue is comfortable, and that comfort will be reflected throughout their entire body and way of going.

For more on tongue evasions and their causes, see our dedicated article on understanding tongue pressure in horses. The British Horse Society and World Horse Welfare also offer excellent resources on equine behaviour and bit-related discomfort.

Bar pressure

The bars of the mouth are the bony ridges in the lower jaw that occupy the interdental space — the gap between the incisors and the cheek teeth where the bit rests. They represent one of the most sensitive and potentially vulnerable pressure points in the horse's mouth. Unlike the tongue, which is muscular and has some capacity to absorb and distribute pressure, the bars are covered by only a thin layer of gum tissue directly over bone. There is no muscle, no fat, and no cushioning — pressure applied to the bars is transmitted almost directly onto the underlying bone.

Bar pressure, applied lightly and correctly, provides the horse with clear, direct signals they can feel and respond to with precision. The sensitivity of the bars means that very little pressure is required to communicate effectively — which is why riders who develop truly educated, sympathetic hands are often able to achieve remarkable lightness. The horse does not need a strong signal because the bars are sensitive enough to feel an extremely subtle one.

The flip side of this sensitivity is vulnerability. Excessive, prolonged, or incorrectly applied bar pressure can cause bruising, inflammation, and in more serious or longstanding cases, lasting bony changes to the bars themselves. A horse with sore or damaged bars will often show a marked reluctance to accept contact, sensitivity when the bridle is put on, and head tossing or evasion when rein pressure is applied. 

Over time, horses that have experienced significant bar pain may develop a degree of desensitisation as a protective response — the tissue becomes thickened and less sensitive — but this apparent tolerance is not a positive development. It is a sign that damage has occurred and that the horse's ability to feel and respond to subtle, correct aids has been compromised.

Bar conformation varies considerably between individuals. Some horses have sharp, prominent bars that are particularly sensitive and require careful consideration when selecting a bit; others have broader, flatter bars that are somewhat more tolerant of pressure. 

The condition and conformation of the bars should always be assessed as part of a comprehensive bit fitting consultation, and any concerns about bar health should be discussed with a qualified equine dental technician or vet.

The British Association of Equine Dental Technicians maintains a register of practitioners across the UK.

Poll pressure

Poll pressure is perhaps the most misunderstood of all the major pressure points associated with bitting, largely because the poll itself is not part of the mouth — and yet it is profoundly influenced by the bitting arrangement and the way in which rein contact is taken and maintained.

The poll is the area at the very top of the horse's head, where the first cervical vertebra — the atlas — meets the skull at the atlanto-occipital joint. This region is rich with nerve endings, highly sensitive to pressure, and critically important to the horse's ability to flex, soften, and work correctly through their topline. The headpiece of the bridle sits directly over the poll, and the pressure it exerts here is influenced significantly by how the horse is carrying their head and neck, and by how the bit and reins are being used.

When a horse is working correctly — in a consistent, sympathetic contact, with the neck stretched forward and the poll as the highest point — the pressure of the headpiece on the poll is evenly distributed and relatively light. However, when rein pressure creates a downward and backward action on the bit, the horse's natural biomechanical response is to raise the head and neck, which increases the pressure of the headpiece on the poll. This poll pressure then acts as a signal that encourages the horse to lower their head — which, when used correctly and in appropriate measure, is part of how correctly fitted equipment and sympathetic riding work together to encourage a correct outline.

The problem arises when poll pressure is excessive, prolonged, or poorly managed. Chronic poll tension — caused by a poorly fitted headpiece, an overtight browband pulling the headpiece into the base of the ears, or a style of riding that creates constant backward and downward rein pressure — can restrict movement at the atlanto-occipital joint and generate a chain reaction of tightness that travels down through the neck, into the back, and through to the hindquarters. 

A horse that is chronically tense through the poll cannot swing freely through their back, cannot engage their hindquarters properly, and will struggle to achieve the softness and throughness that correct training requires. Research published in the Equine Veterinary Journal has highlighted the significance of poll tension and its relationship to both equipment fit and ridden horse welfare.

Poll sensitivity also has a significant psychological dimension. Many horses that have experienced discomfort or pain in the poll region become defensive and anxious when anything approaches their head and ears. This anxiety can persist long after the original source of discomfort has been addressed, and rebuilding confidence requires patience and a genuinely sympathetic approach.

Lip and corner of mouth pressure

The lips and corners of the mouth are the most externally visible pressure points associated with bit fit, and among the most immediately sensitive. The skin at the corners is thin and delicate, and it is here that the rings or cheekpieces of the bit make direct contact — meaning that width and cheekpiece design have a direct and immediate impact on comfort in this area.

Correctly managed lip and corner pressure provides the horse with clear positional signals — a gentle upward pressure at the corners communicates the height at which the bit is sitting and gives the horse a consistent point of reference for the contact. When this pressure is light, even, and consistent, most horses accept it willingly and without tension.

Problems arise when pressure at the corners becomes excessive, uneven, or abrasive. A bit that is too narrow pinches the lips against the rings or cheekpieces, creating sharp, painful pressure the horse cannot avoid. A bit that is too high in the mouth creates constant upward pressure at the corners that never allows any relief, leading to tension, resistance, and in time, thickening of the skin in the affected area. A bit that moves excessively from side to side creates friction and rubbing that quickly produces soreness and, in established cases, wounds and scar tissue that further compromise the comfort of any future bitting arrangement.

The corners of the mouth are also a key area for observing the horse's overall response to their bitting. A horse that is relaxed and comfortable will have soft, mobile lips; a horse that is tense or uncomfortable may show tightness in the lips and muzzle, a fixed or braced jaw, or a reluctance to chew or soften. These subtle signs of oral tension are valuable indicators of overall comfort and should always be assessed as part of any bitting or bridle fitting consultation.

Chin groove and curb pressure

The chin groove — the groove that runs along the lower jaw just behind the lower lip — is the pressure point associated with curb chains, curb straps, and bit designs that incorporate a curb action. When correctly fitted and used, a curb chain limits the rotation of the shank and creates a squeezing action that distributes pressure between the poll, the bars, and the chin groove simultaneously. This combined action, used with educated and sympathetic hands, can be a very effective means of communication that encourages the horse to soften through the jaw and poll together.

However, the chin groove is sensitive, and curb pressure applied incorrectly, too severely, or without an understanding of how it interacts with the other pressure points in the system can cause significant discomfort. A curb chain fitted too tightly will apply excessive pressure to the chin groove before the bit has had the opportunity to act through its intended range of motion, creating a sharp, abrupt action that many horses find uncomfortable and that can lead to evasion, jaw tension, and resistance. Conversely, a curb chain fitted too loosely will not engage until the shank has rotated well beyond its intended range, creating a sudden, uncontrolled action that is equally unhelpful.

Curb chains should be checked regularly for damage, sharp links, or wear that might cause unnecessary discomfort, and should always lie flat and evenly in the chin groove with the links flat against the skin. British Equestrian provides guidance on the correct fitting of curb chains as part of their tack and equipment standards.

Nose and facial pressure

The nose and face are not directly acted upon by the bit itself, but the noseband — which forms part of the overall bridle and bitting system — applies pressure to the nasal bone, the soft cartilage of the nose, and the sides of the face. This pressure has a direct and significant influence on how the horse responds to the bit and accepts contact.

The primary function of a noseband in the context of the bitting system is to provide a degree of stability and to prevent the horse from opening their mouth excessively and evading the bit's action. However, when a noseband is fitted too tightly, it restricts the horse's ability to move their jaw — preventing the chewing and softening that are fundamental signs of relaxation and correct acceptance of contact — and creates pressure on the nasal bone and sides of the face that can cause discomfort and anxiety.

Research into noseband tightness and equine welfare has been extensive in recent years, with studies from institutions including University College Dublin consistently demonstrating that overtightened nosebands are associated with elevated stress indicators, increased eye white visibility, and other signs of negative emotional states in horses. This research reinforces the importance of always fitting nosebands with the horse's comfort at the forefront of the decision.

Facial nerve pressure — from cheekpieces, nosebands, or other bridle components sitting incorrectly on or near the facial nerve pathways — can cause discomfort, head tilting, resistance to the contact on one rein, and in more serious cases, facial numbness. 

The facial nerves run along defined pathways on the side of the horse's face, and a thorough bridle and bit fitting consultation will always assess the positioning of all components in relation to these pathways. For a deeper look at how noseband fit interacts with the bitting system, see our article on how a correctly fitted bridle affects your horse's comfort and performance.

The temporomandibular joint — where everything connects

No discussion of bit pressure would be complete without the temporomandibular joint — the TMJ — which connects the lower jaw to the skull and sits at the intersection of many of the pressure points discussed in this article. The TMJ is responsible for the opening, closing, and lateral movement of the jaw, and its health and freedom of movement are fundamental to the horse's ability to accept the bit, soften through the jaw, and work correctly through the topline.

When the TMJ is functioning well, the horse is able to chew, soften, and mouth the bit gently — all signs of relaxation and correct acceptance of contact. When the TMJ is under inappropriate pressure, restricted in its movement, or affected by dysfunction from longstanding bitting or equipment problems, the consequences can be far-reaching. TMJ dysfunction is associated with jaw asymmetry, uneven dental wear, poll tension, one-sided stiffness, and a wide range of training difficulties that may persist even after the original equipment issue has been resolved.

The health of the TMJ is intimately connected to dental health, and any horse presenting with signs of TMJ dysfunction should be assessed by a qualified equine dental technician or vet alongside a professional bit and bridle fitter. Regular dental care, combined with appropriate equipment fitting, is the most effective way to protect TMJ health over the long term. Further information on equine dental care is available through the British Equine Veterinary Association and the British Association of Equine Dental Technicians.

Bringing it all together

The pressure points described in this article do not function in isolation — they are interconnected parts of a complex system, and changes in pressure at one point will almost always have consequences elsewhere. A bit that creates excessive tongue pressure may cause the horse to brace their jaw, which creates tension through the TMJ and poll. A poorly fitted headpiece generating chronic poll tension will restrict the horse's ability to soften through the jaw, making it impossible to achieve true relaxation in the mouth regardless of how well the bit itself is chosen. Noseband fit interacts with mouth pressure; bar condition is linked to dental health; lip and corner soreness affects the horse's confidence and willingness long after the physical soreness has healed.

This interconnectedness is precisely why professional bit and bridle fitting is so valuable, and why it cannot be reliably replaced by measuring tapes, online guides, or well-intentioned guesswork. A professional fitter brings together a thorough knowledge of anatomy, equipment design, and training principles to assess the individual horse and their bitting arrangement as a complete picture — identifying areas of concern and making recommendations that address the whole horse rather than individual components in isolation.

Key takeaways

✔ The tongue is the primary pressure point for most bits — excessive tongue pressure causes evasions that are frequently misread as training problems

✔ The bars are bone covered only by thin gum tissue — bar pressure transmits almost directly onto bone, and damage can cause lasting desensitisation that compromises the horse's ability to respond to subtle aids

✔ Poll pressure is influenced by the bitting arrangement even though the poll is not part of the mouth — chronic poll tension has consequences throughout the entire topline

✔ Lip and corner pressure is the most visible indicator of bit fit — soreness, asymmetry, and thickening of the skin all warrant investigation

✔ Curb pressure must be carefully managed — a chain fitted too tightly or too loosely produces an action that is uncomfortable and counterproductive

✔ Noseband fit is part of the bitting system — overtightening restricts jaw movement and is associated with measurable stress responses in horses

✔ The TMJ connects jaw freedom to throughness throughout the whole horse — TMJ dysfunction from bitting problems can persist long after the equipment issue has been resolved

✔ All pressure points are interconnected — changes at one point have consequences throughout the whole system

The case for professional bit fitting

Understanding bit pressure is the first step. Applying that understanding accurately to an individual horse — assessing their specific anatomy, sensitivities, current equipment, and way of going, and translating all of that into genuinely 

appropriate recommendations — is the work of a professional fitting.

At The Fitted Horse, every bit fitting consultation assesses all the major pressure points and their interactions, bringing a thorough knowledge of bit design and equine anatomy together to arrive at recommendations that are genuinely tailored to your horse as an individual.

Book a bridle and bit fitting consultation →

Further reading: Understanding tongue pressure in horses | A complete guide to bit mouthpieces | The complete guide to bit cheekpieces | Choosing the right bit for your horse's mouth conformation | Why a correctly fitted bit matters