Bit action explained
Most equestrians have good knowledge of saddle fit, nutrition and hoof management. However when it comes to the bit, few understand how it works mechanically, says Dr Caroline Benoist.
Ill-fitting and inappropriate bits can cause conflict behaviours that lead to physical and physiological problems throughout the whole horse.
Regrettably, most reliable information regarding bits – at least that within the constraints of equine science - is inaccessible to the lay rider. Riders are therefore increasingly seeking the help of a professional bit-fitter.
Fortunately, we are seeing saddle-fitters becoming interested in bit and bridle fitting as an addition to fitting saddles. I view this as good progress in terms of the comfort and welfare of the horse. Looking at the whole picture, rather than isolating each piece of tack is beneficial because a perceived saddle fit issue might stem from the rider’s use and choice of bit. It makes sense to evaluate everything at once.
Those seeking rigorous, scientifically backed training will be hard-pressed to find it. However, with the recent surge in demand, some formal training programmes have emerged.
The Neue Schule (NS) Academy, for example, has drawn together much existing lorinery research and, along with its own research findings, put it into a manageable format through a series of on-line courses. The Foundation-level course is open to anyone interested in learning about bits from a purely mechanical perspective. Those seeking a deeper understanding must qualify to access the remaining courses.
NS Academy courses are approved by Lantra and currently available to equine degree students at Bishop Burton College and Nottingham-Trent University. The International Education for Equine Bit Fitters (IEEBF), located in the Netherlands, offers various courses for equine bit-fitting. The two work very well together.
So, how does a bit work?
The bit is examined in two parts since cheeks and mouthpieces have separate functions.
A mouthpiece affects the tongue, lips, bars and hard palate. The cheek-type determines the degree of rotation of the mouthpiece and degree of any poll pressure produced when rein tension is applied.
Cheek-types and poll-pressure
Snaffle bits operate primarily on the mouth. An exception is the running gag cheek for which approximately 30% of the rein forces transfer to the poll. Like all snaffles, gag cheeks act into the corners of the mouth and, because they are a pulley, amplify the rein forces here. This can be quite severe, especially when the horse’s neck is stretched out.
By contrast, the Baucher cheek provides a poll-relief effect by lowering tension in the cheekpieces (See Photo 1). Poll pressure from a Baucher is impossible because there are no forces exerted below the mouthpiece.
Lever bits - those with extensions above and below the mouthpiece - produce varying degrees of poll-pressure depending on the ratio of the upper and lower shank lengths.
Surprisingly, with the curb and bridoon acting together, we see increased poll pressure compared with when the curb acts alone. This is potentially caused by the bridoon trapping the cur.(See Photo 2).] After researching this, Neue Schule developed the Turtle Tilt - a curb designed to reduce trapping by creating more separation between the bits.
A mouthpiece first influences the tongue which fills the entire oral cavity. As it is positioned against the palate, the tongue must relax and compress to accommodate a bit.
Choosing an appropriate mouthpiece can be daunting. What we consider to be of utmost importance is comfort and that comes, in the first instance, from even pressure distribution on the tongue.
Anatomically sensitive designs with broad surfaces allow for more tongue room and pressure distribution. Setting the mouthpiece at an angle to the cheek allows it to remain flat on the tongue under rein tension and prevents anything from pressing in.
With sufficient rein tension, a mouthpiece rotates, causing features such as loops, lozenges and plates to reposition their orientation relative to the tongue. One stark example of this is the French Link mouthpiece. When rotated into its working position, the thin edge of the plate presses into the tongue. On the other hand, the plate of an original and correctly fitted Dr Bristol lies flat on the tongue. This is in direct contrast to popular belief, and a prime example of misinformation. (See Photo 3).
Jointed mouthpieces produce a nutcracker action which does not, as popularly understood, cause palate pressure. Rather it creates a squeezing action around the tongue, the severity of which depends on the number of joints. A single-jointed mouthpiece produces the strongest effect, while the multi-jointed Waterford has almost none.
Straight bar or mullen mouth mouthpieces are a good option if jointed bits are to be avoided. These act more directly over the bars, which - unless the horse draws its tongue back or sticks it out sideways - are typically covered by the tongue.
The severity of bar pressure depends then on the thickness and width of the horse’s tongue, steadiness of the rider’s hands and amount of rein tension applied.
Anatomy and rider actions
The horse’s tongue is connected to the hyoid bone, located in the throatlatch area. The hyoid anchors the tongue and is itself anchored by muscles attached to the sternum and scapula. Because the tongue is directly connected to the shoulder, it must be treated with care or the gaits will suffer.
When it comes to bits, riding style can significantly impact the horse’s way of going – especially when a rider is too heavy handed.
Technology can help. Various rein tension devices are available and can play an important role in moderating ‘weight’ in the reins and improving balance in the contact. Avansce Ltd (www.avansce.com) is developing one such device that records not only these basic parameters but also the degree of acceptance of the contact in the horse/rider partnership.
Proper bridle fit is equally important. A tight browband causes temporomandibular joint (TMJ) discomfort. While a tight noseband prevents the horse from sliding the jaws over each other, causing TMJ dysfunction.
The TMJ is a hinge connecting the jaw to the skull. When impaired, it not only affects mastication but also proprioception – the sense of spatial awareness; thus coordinated movement suffers.
Choosing a bit
Bitting choice should be based on the horse’s anatomy, preferences, and riding style. Knowledge is power; ask questions and read reputable, peer-reviewed, material.
My personal philosophy is to choose a cheek for control, if necessary; and a mouthpiece that is soft and comfortable.
Thick mouthpieces distribute pressure over a greater area compared with thin ones. However, the lowest average distance between a horse’s upper and lower jaw is 25mm. Thick mouthpieces can have a diameter of up to 23mm, but thin mouthpieces are more severe in terms of pressure.
So opt for a mouthpiece that distributes pressure evenly and is ergonomically designed to suit the mouth and minimise bar pressure. (See Photo 4).
Double-jointed mouthpieces are less likely to cause lip injuries as they sit more symmetrically on the tongue than single jointed ones. However, with uneven rein tension, the bit is pulled to one side increasing the likelihood of pinching the lips and injuring the bars.
Double bridles require a bit more thought. Ensure there is enough space between the curb and the bridoon. Not only is there a risk of pinching the tongue between the two bits, but when they overlap, conflicting signals are sent by inadvertently activating the curb through the bridoon.
Curb bits with ports allowing for tongue room can contact the palate. Wide and high ports give more room, however we often see ports that are narrow and not likely to offer much tongue relief.
Some vertical ports are 3cm high. The average depth of the equine hard palate is 1-2cm, thus contact is inevitable. The severity of contact depends on the depth of the palate, direction of the port - backward-facing ports are less likely to interfere - and the strength of the rider’s rein aids. Also, the greater the tongue relief a port provides, the greater the pressure on the bars will be.
Awareness of these potential problems should help riders choose what is right for their horses. It should also serve as a reminder to check the mouth and bit often for signs of bruising, cuts or abrasions.
Decide on a material. Options range from synthetic to different combinations of metals. Synthetic bits can be abrasive but are soft on the teeth. Most metals are hard and can damage tooth enamel. Softer metals, such as copper alloys, are a better choice if the horse chomps the bit.
All mouthpieces, whether metal or synthetic, must be regularly inspected for wear to avoid injuries (See Photo 5).