Halters, bridles, reins, and martingales serve a variety of biomechanical functions. Here’s what you should know.
By Christa Leste-Lasserre, MA, The Horse: Your Guide To Equine Health Care
Any visit to your neighborhood tack shop will prove that equine equipment is certainly not limited to saddles and bits. So we’ve reached out to equine professionals and scientists worldwide to get a grasp on halters, reins, martingales, and other kinds of accessory head tack.
Halters
Halters strap to a horse’s head and are used for leading and tying the animal (as opposed to a bridle which has a bit and is used for riding). Think of a halter as a collar for horses. In fact, in some areas halters are referred to as “head collars.”
When you’re looking to purchase a new halter for your horse, you’ll find a large selection in a variety of makes, models, materials, and colors. Following are a few of the different halter options you can choose from.
Traditional Leather Halters: Flat, Padded, and Rolled Traditional leather halters are constructed of cowhide, and the pieces connect via metal or brass fittings and buckles. These halters are often highly adjustable at multiple points for a customized fit. Features can include padding, adding comfort and providing a stylish look, or rolled leather for more precise pressure and extra control.
Some halters clip to fasten at the throatlatch, which can make them convenient for grooming and offer the option of slipping the halter over the head rather than opening and closing the crownpiece (the part that goes over the horse’s head, behind the ears). While durable, leather halters will usually break under pressure, such as when accidentally caught on a fence or other object. This is considered a safety feature of leather halters.
Flat Nylon Halters Flat halters made of nylon are similar in structure to traditional leather halters. The webbing material is inexpensive, strong, versatile, and a popular choice for regular barn use. Their synthetic material wears well and comes in a rainbow of colors but is very difficult to break should a horse become stuck on a stationary object.
Some flat nylon halters come with leather crownpieces or tabs that are designed to break under pressure. These halters are usually sold as “breakaway” or “safety” halters.
Grooming Halters Grooming halters are similar to leather and nylon halters, but do not have a throatlatch. This makes for easy grooming of the face and allows the halter to easily slip over the head if a horse panics and pulls back when tied. These halters are not designed for training or in-hand work.
For added versatility, consider getting a convertible grooming halter that offers a detachable throatlatch.
Rope Halters Rope halters are training tools used by many natural horsemanship trainers. As the name implies, these halters are made from rope (most commonly braided nylon cord) and are tied together rather than constructed using hardware connections. Also, instead of buckling, rope halters tie to fasten.
Many rope halters include strategically placed knots over nose and/or poll pressure points for added control of the horse. Like their flat nylon halter counterparts, rope halters are durable and come in a variety of colors. The lack of hardware at cheek pieces make them less than ideal for cross-tying horses.
Show Halters Think of show halters as horse jewelry. They are designed for competition, such as in-hand halter and showmanship classes, and different breeds have different show halter requirements, styles, traditions, and trends. A show halter for an Arabian, for example, is different than what you would use on a stock horse. Show halters often feature silver, crystals, or beading.
Check with your show association or a local trainer experienced trainer to make sure you’re getting the correct type of show halter for your breed and discipline.
Bridles
The primary head accessory when riding a horse is the bridle. The bridle’s purpose isn’t limited to holding the bit and noseband in place; it also serves an important biomechanical function. Many riders desire appropriate flexion in their horse’s poll, an indicator that the horse is accepting the bit in his mouth and heeding the rider’s cues. Depending on the type of bit used, pressure applied across the horse’s sensitive poll area can vary greatly. It is generally thought that the longer the shank (the side or cheek piece) of the bit, the greater the pressure the bridle applies to the poll, although researchers have not proven this, says Hayley Randle, PhD, associate head of the School of Animal and Veterinary Sciences at Charles Sturt University, in Australia.
Another considerably important piece of the bridle is the noseband, says Roepstorff. The amount of rein tension a rider uses to maintain contact with the bit varies significantly with the tightness of the noseband, Randle explains. The topic of nosebands and all the different varieties available could also comprise its own article. But generally speaking, researchers recommend keeping a two-finger-sized gap between the noseband and the horse’s nose. Tight nosebands exert such pressure on the sensitive nasal bones that the FEI passed a rule stating that to protect equine welfare, nosebands worn in competition must not be tighter than the width of two fingers above the nasal bone.
Likewise, bitless bridles apply increased pressure to the head’s hard tissues, says Hilary M. Clayton, BVMS, PhD, Dipl. ACVSMR, MRCVS, McPhail Dressage Chair Emerita at Michigan State University and president of Sport Horse Science, in Mason, Michigan. The mechanics of bitless bridles leverage increased pressure to the horse’s poll and nose, she explains.
Draw Reins
Draw reins run from the saddle or the girth through the bit and up to the rider’s hands. The forces the draw reins apply depend on their starting point (between the horse’s front legs or on a low or high part of the saddle), says Roepstorff. The lowest position—attached to the girth between the front legs—supplies the most dramatic effect. Draw reins’ mechanics are twofold, he explains. First, running through the bit, they work as a pulley and double the force of the rider’s hands. Secondly, they change the direction of the force by pulling down on the jaw and tongue instead of back.
Roepstorff and his team have studied the kinematics (measurement of body motion) of draw rein use over several years, and they confirm that these are potent tools. When riders rode with draw reins only, the horses’ neck angles decreased 20-25%. But neck angle alone doesn’t create collection—remember that weight-shift to the hindquarters and balance do. Interestingly, with draw reins alone the horses had tightly tucked heads to the point of hyperflexion, and their weight tended to shift to the forelimbs. “This is the exact opposite effect of what you want from these reins,” he says.
When horses were ridden with draw reins and normal reins combined, however, collection was achieved. The head angle only decreased 4-6%, but the hock and hip angles and the swing and propulsion of the legs suggested superior hind-limb loading. Roepstorff’s word of caution? “Always complement your draw reins with regular reins at the same time,” he says. “Never use them with a shanked bit, which multiplies the force. And always use them under the guidance of a skilled trainer.”
The hazards of improper draw rein use include forelimb loading that can lead to increased risk of developing lameness, explains Roepstorff, along with long periods of hyperflexion or discomfort that can lead to psychological problems such as conflict behavior and an unwilling attitude towards work. It can also cause a serious psychological condition very similar to learned helplessness in humans, says Randle.
“The draw rein makes you very strong,” Roepstorff says. “It’s a razor in your hands.”
In a nutshell: Use them correctly and under the guidance of a skilled professional, and you could get the collection you’re looking for. Use them incorrectly, and you might cause your horse lasting damage—both physically and mentally.
Running Martingales
Running martingales attach at the girth and run up between the horse’s front legs, where they branch out into two parts with a ring at each end; regular reins run through these rings. Different martingale varieties supply effects similar to the running martingale, including the English-style running martingale and the Arabian training martingale.
Riders should adjust their horses’ bridles properly—and we’re not just talking about the traditional “three wrinkles in the corner of the mouth” rule, says Heleski. “The depth of a horse’s mouth will impact how many ‘wrinkles’ end up forming,” she says. And according to Clayton, the fit also depends on the kind of noseband. Used with a cavesson (when the noseband is attached to its own headstall or crownpiece, held independently of the bit) or no noseband, the bit should fit into the corners of the lips, she says. With drop nosebands (which encircle the nose around the chin groove, as opposed to just below the cheekbone), the cheek pieces should be adjusted a little shorter so that the bit rings don’t hang loose.
These martingale types all apply a slight lever effect but not the pulley effect of draw reins, Roepstorff explains. Their most significant impact is the change in direction of force, angling the bit’s pull slightly downward instead of directly backward or even upward, if the horse’s head tends to rise.
Heleski and her team studied the use of the running martingale and found that it can also be a beneficial tool for correcting human error. She has confirmed this in her own experience as a riding instructor. “Martingales can help buffer the effects of occasional mistakes by riders’ hands,” she says. “Although we don’t yet have the science to prove it, it does appear that more consistent, slightly greater tension is better for the horse than lighter tension with sporadic large tensions.”
Just as with most tack, fit is key to proper martingale use. Heleski says a short martingale pulls the horse’s head and neck lower, causing discomfort without creating collection—an effect similar to the phenomenon seen when riders use draw reins alone. And, regardless of the martingale’s size, a rider should only consider it a short-term training aid, using it until both he or she and the horse are able to work without it. “Martingales shouldn’t be a long-term crutch,” she says. “But I truly believe they are such a mouth-saver for horses.”
Even so, Heleski cautions against using them with horses that are prone to buck or run off because the rider loses the leverage and angles necessary for emergency control.
Chambons, Standing Martingales, and Tiedowns
Chambons, standing martingales, and tiedowns all work on the same principle: using a fixed line connected at the girth between the legs to prevent the horse’s head from rising too high. While standing martingales and tiedowns function by applying pressure only to the poll, chambons run a line down from the poll along the cheek for more distributed pressure across the head.
“Standing martingales (and tiedowns) will not improve a ‘headset’ but can help keep the horse from flinging up its head, for example during jumping, so it can add an element of human safety,” says Heleski.
They can be dangerous for horses in certain situations, however. “Riders need to give their horses time to adapt to these tools if they choose to use them,” Heleski says. “And if they ever cross a river with them that might get deep, they must remove or unhook them to prevent drowning.”
Side Reins
Side reins attach from the bit directly to a saddle, girth, or surcingle at various levels. Trainers and riders typically use side reins during groundwork only, especially longeing, though they do employ them on longeing vaulting horses. Side reins are fixed at a set length; the horse can vary the tension level by changing the position of his head. However, some other things still affect that tension. Clayton and her team studied the effects of side rein length and elasticity at the trot. They confirmed what might seem logical: As the reins tighten, the tension increases. They also proved that elasticity matters: The more elastic the rein, the lower the maximum and average tension. But what that means for trainers is a somewhat complicated calculation that scientists haven’t solved. Do short but very elastic side reins create less or more tension than long, inelastic reins?
“Perhaps most interesting was the fact that horses were more willing to take and maintain a contact (with the bit) with a core elastic side rein (that which sports an elastic insert),” Clayton says.
Marie Rhodin, DVM, PhD, associate professor in equine clinical biomechanics at the Swedish University of Agricultural Sciences in Uppsala, studied side reins’ effects on horses’ stride length. She found that when horses’ heads were fixed high, stride was shortened at the walk and back flexibility was reduced at both the walk and the trot. However, if horses’ heads were fixed low, both stride and back flexibility increased. Randle says her team found similar results in their studies.
Head tack accessories aren’t just meant to hold this part here or prevent that part from moving there. The kinematics and biomechanics behind these tools are complex, and riders should give them significant consideration. Research on head tack accessories is new, but as it progresses, riders can rely on the knowledge of skilled professionals to ensure that the accessories they choose, and the way they apply them, are the right choice for their horses. 
Reprinted with permission from The Horse: Your Guide to Equine Health Care/TheHorse.com. Find more veterinarian-approved horse care information at TheHorse.com.
