Traditional Dressage / articles - For the Good of the Horse & Rider
The Double Bridle

Extract from the very good book written by Waldemar Seunig, "Horsemanship" (1956)
"If the training of our horse has reached the point where it an assume the degree of collection corresponding to its conformation, familiarizing it with the action of the bar bit will have no harmful effect.
If there are no compelling reasons for riding the horses fully bridled, it will always be better to recondition it on the snaffle.
One reason is that many faults of posture and contact with the bit manifested when riding with a curb bit will indicate how such reconditioning should be done.
Even in the Spanish Riding School of Vienna,  the older horses are often ridden with snaffle bits excepts on official occasions. ("this text was written 60 years ago, we do not now now".)
Such reconditioning is feasible only because of the action of the jointed snaffle mouthpiece, as will be explained later. 

This reconditioning is facilitated when the pressure exerted upon the horse's mouth by the rider's hands is not multiplied.
The rider is better able to test his aids, therefore, than when he uses the curb bit, whose lever action multiplies the force of the hands many times before it reaches the load (mouth).
At the outset, however, it will be well to retain the thicker snaffle bit employed up to now instead of the usual thin snaffle, even for the fully bridled horse.
Once the gymnastic training of the horse has achieved a very high level, so that its suppleness and impulsion ensure perfect collection, using the curb bit - especially with the snaffle released - will enable us to refine and perfect our reins aids still further, and establish a steady, elastic connection between the rider's hands and the horse's mouth, such as can be achieved only with the lever action of the curb.
Familiarizing the young horse with the curb bit will have to be done principally at the ordinary gaits, on long lines in the open air, with the curb bit completely inoperative at the start.
At these lively, long-striding gaits we will extend the horse and very gradually let it reach the bar bit, to which is attached a very long curb chain or none at all for the present.
After a few easy-going rides in the open air, with the horse becoming supple as a result of its vigorous strides in contact with the passive hands, the curb chain is attached so as  to produce real lever action.
Then, the entire course of training described above, from the stage of suppleness onward, is repeated in the riding hall with the same free carriage.
Collecting aids are applied only when the young horse has trustingly accepted the unusual bridle and is positively in hand.
When this procedure is followed, all the faults described below (which arise only because the horse was not ready for the curb bit or defended itself against the constrain and pain that the new sharp bridling caused it by curling up, holding back and resisting) will be avoided.
If overhasty"familiarisation" with the curb bit has frightened the horse away from the bit, long and patient work will be required to repair the mistakes committed and to regain the forward advance, i.e. the vigorous strides and supple extension towards the bit. Here too the apparently shorter path is not the quickest way to reach our goal.
We think the best way of indicating the nature of the curb bridle and its action is to discuss some of the mistakes that can be observed everyday in the use of this bridle. Discussion of these mistakes and their consequences for gait and posture will automatically tell us how to avoid such difficulties in the training of our horse.
Horses that are not ready for the curb bit

The action of a horse is refined and perfected by the use of the curb bit, owing to its more positive and steadier action upon the horse's lower jaw, which does not allow any incipient stiffness to be manifested. The horse must be prepared for this bit, however by work on the snaffle. But false gait and false contact with the bit are manifested much more clearly when we try to use a full bridle too soon than when we work the horse with a snaffle bit. Why?
The curb bit operates as a lever, which is intended to control the load (the evenly loaded horse in a state of acquired equilibrium) from the point at which this force is applied (the rings on the branches of the bit) through the neck, the spinal column, the pelvis, the haunches, and the hocks to the pastern joints.
This force can be transmitted down to the tips of the hoofs of the hind legs without hindrance, however, only if the horse is supple, i.e., if the transmission line is not interrupted, so that the force cannot escape upward, downward, to the side, or in front or be blocked anywhere.
For this first condition to be satisfied the horse must be extended to the reins and be evenly loaded, that is, its spinal column must be adapted to the straight or curved line that it is following at the time.  Moreover it must always be ready to assume the additional longitudinal flexion required for collection, work at the gallop, and work on two tracks.
The second condition is satisfied if prior work with the snaffle has already established an equestrian balance that provides the horse with such posture that the lever force of the branch of the curb bit is not blocked in the region of the pelvis but passes onto the haunches, which have been rendered able to carry the load and to bend as a result of flexion work.
The horse is ready for the curb bit if the foregoing two conditions are satisfied, but they can be satisfied only if the horse moves forward resolutely and vigorously, in steady contact with the bit and positively obedient.
The horse is not ready for the bit, however, if it opposes the lever action by active or passive resistance.
This recalcitrance is always do to faulty preparation, if we except feelings of pain produced by poorly fitting, wrong mounted curb bits and curb chains and by the rider's generally defective seat and guidance.
This recalcitrance will be manifested in evasion, stiffness, or distortion of the lower jaw, the neck, and the back, produced by impure, stiff, or dragging action of the hindquarters, which is always the principal source of resistance in the other parts of the horse's body.
So if the horse is not one of the very, very rare specimens that combine perfect conformation and ideal harmony of weight and muscular force with a soul that wished nothing better than to comply with the rider's desires as soon as it has understood them, we will do well to fit a curb bit only after two or more years of training, provided that training began when the horse was four and a half years old.
If we do not obey this golden rule, and the reins are not in the hands of a real master but merely of someone who is self-appointed to that rank, premature use of the curb bit will merely achieve the contrary of what was intended.
The danger then arises that the gait, which was supposed to grow longer, more expressive, and nobler as a result of dressage, is lost.
Contact with the bit becomes unsure and unsteady. The horse is leaning on, over, or behind the bit, for it no longer reaches forward to the bit willingly through its neck and poll.
But if it does not do so, the rider's control of its hindquarters is imperilled and obedience with it.
The equestrian poise already achieved by work on the snaffle will be lost more and more, for once the hind legs no longer reach forward smoothly and fluently towards the centre of gravity, but oppose the lever action, staying behind or dragging sluggishly, the inadequately supported forehand will have to carry a greater share of the load.
Then it hampers the free extension of the forelegs in equestrian balance, and the horse falls upon its shoulders in an expressionless gait.
Riders who are not ready for the curb bit
We often see groups of young riders, accompanied by an instructor, taking their first cross-country rides on bridle paths and through fields in the outskirts of large cities. This picture loses something of its charm when we notice that some of them are riding their deserving, experienced livery horses with curb bits. Most of these ladies and gentlemen are not ready for the curb bit.
A prerequisite for learning how to ride a horse with a bar bit (a solid mouthpiece, therefore called "bar" is a supple, soft, and independent balanced seat plus the ability not only to use aids as signals but to apply them effectively.
Once the good seat has produced soft and steady hands, real "glass-of-water-fists", as Monteton calls them, which absorb all the shocks imparted by the movement in the elbow and shoulder joints, the time may be ripe for beginning to ride with the curb bit.
Theoretical knowledge is a far cry from horsemanship
We must, of course, be completely familiar with the nature, actions, and objectives of curb bits, which differ fundamentally from the snaffle.
We must be familiar with the fit and position of the different parts of a curb bit and with the infinite variety in sizes of bars, ports, curb grooves, mouth angles, and the like.
We must know that when we use a branched lever with the bar bearing on the lower jar of the tongue, which are directly connected to the entire nervous and muscular system, the horse feels many times the force applied by the rider's hands.
 We should always bear in mind this fundamental difference between the action of the curb bit and the milder action of the snaffle, in which there is a one-to-one ratio between power and load.
The second fundamental difference follows from the fact that the curb mouthpiece is not jointed, but is fixed in position by the opposing curb chain and acts upon both sides of the lower jaw at once, even though it may be made to act somewhat more strongly upon one side than the other if necessary. In this manner it flexes the joints of both hind legs.
Much can be learned from observing a master rider in order to see what contact with the curb bit looks like. The feathering of the bar should indicate that its reins are in light contact as a result of the horse's reaching for the bit, relaxed, yet vigorous and trusting.
Knowledge alone is merely a preparatory step to the conscious acquisition of practical ability, however. This takes place only when we ourselves sit in the saddle on a well-made horse and learn correct contact with the curb bit that is fitted according to regulations, for theoretical knowledge is a far cry from horsemanship.
There will be always moments when the horse will try to escape even loading on all four legs and try to render the curb reins inoperative by bending its body.
That constitutes the best opportunity to learn in practice, under proper guidance, that uniform contact with the bit can be restored only by the corresponding reins of the bridoon, since the curb bit, with its solid mouthpiece, makes no provision for purely one-sided action.
Important though it is for every horse to have a curb bit that fits and is placed so as to act correctly, let us state in conclusion that faultless riding with a curb bit depends less upon the form of the bit than upon the direction of the skeleton, which prepares the horse for accepting the bit.
It is, however, just as true that when a well-made horse of good conformation has a curb bit that does not fit it individually, it cannot move as well as when it is properly bridled."