The Direct Rein of Opposition
The Direct Rein of Opposition is by far  the most misused and abused rein aid of the five. This is a rein of  opposition, which means it blocks the horse’s impulsion on the side used  – or, because this aid can be used simultaneously on both reins, blocks  both sides – and transfers the horse’s balance backward toward the  hindquarter on the side where the rein is used. As with all reins of  opposition, this is an incredibly powerful aid and, used improperly, can  be the cause of significant – and justified – resistance from the  horse, perhaps more than any other rein effect. 
 
This rein has a powerful stopping and/or collecting effect on the  horse in that it causes the horse to re-balance himself toward one or  both hindquarters while opposing forward impulsion. The effect of  this rein is such that, when applied to one side, depending on the  strength of the aid relative to the amount of impulsion, the horse may  turn his head slightly in the direction of the rein due to the back-up  of energy created by its opposition. Because this opposition blocks the  thrust of the related hind leg, the horse may have a tendency to shift  his hindquarters slightly to the outside; however, these are side  effects, and not primary responses. When two reins are used together and  the forward thrust from both hinds is opposed, the horse will halt or,  if the action is sustained, rein back. 
 
Where riders run into trouble with this rein is that many trainers,  including those at the highest levels in both the H/J and Dressage  worlds, inexplicably believe this rein should be used while riding the  horse forward, and particularly for creating bend, turning and circling,  etc., often countering its tendency to displace the hindquarters  outward with a strong opposing outside leg aid.  At the very least, this  amounts to a severe clashing of the aids, as the rein is creating one  effect while the leg must be used to counter it.  Another instance of  clashing the aids is when the direct rein of opposition is used in  conjunction with a forward-driving leg and/or seat, as the hand(s) and  legs are completely at odds with one another; the hand is telling the  horse “whoa” while the legs are telling the horse “go.” With such  contradictory commands, the horse naturally becomes confused and even  resistant, and sooner or later the horse will give up and begin to  ignore (i.e. “resist”) one or both of these aids; here, “resistance” is  just another word for the unfortunate horse trying to tell the rider, “I  don’t understand what you want” or “I can’t do what you’re asking.”  In  extreme cases, the horse will blow up and rear, buck or otherwise try  to eject the rider. 
 
 Despite what some misguided trainers and manuals of equitation say, the Direct Rein of Opposition is not a turning rein. 
This rein can create longitudinal flexion and collection, but should not be used for lateral flexion. For  example, rather than being the inside rein of a turn, its effect is  better suited for occasional light use as an outside rein, re-balancing  the horse on his outside hind, shortening the frame and controlling  speed.  However, as with all reins of opposition, it is to be used  sparingly and with awareness and sympathy. 
 
Technique:
The  hand comes to a position somewhere in front of the rider’s hip and  resists.  The rider does not pull back on the reins, but simply closes  the fingers and offers resistance. 
 
Perhaps this would be a good place to discuss two important  concepts from the famous, if controversial horseman, François Baucher:  the “fixed hand” and “hand without legs, legs without hand.”  Not all of  Baucher’s theories and practices have much place in modern equitation,  particularly his earlier practices and those which have led to the  modern exercise of “rollkur.”  However, these two concepts were  revolutionary in their day and have stood the test of time in that they  can be adapted to everything from Dressage to H/J riding and Natural  Horsemanship. 
 
The fixed hand,  as I interpret it for modern equitation, is key to the Direct Rein of  Opposition.  Contrary to what its name seems to imply, the fixed hand  does not mean setting the hand in an unyielding contact. Rather, it is a  practice of holding the hand in place momentarily while giving a rein  aid, closing the fingers and allowing the horse to relieve the pressure  of the rein on his own. In other words, as the horse gives to the  pressure of the rein, the hand remains in place to avoid a recoil  effect. If one is able to pull a horse’s head in one direction or  another, it means that the horse is giving to the aid (even if perfect  relaxation is absent.)  If the hand (and therefore the pressure) is  following the horse’s mouth backward or sideways as he gives, the horse  is not being rewarded for his correct response and the rider runs the  risk of inadvertently punishing the horse's correct response; the horse  is only rewarded when the rider gives a more dramatic release with a  forward movement of the hand, often only lessening the existing  pressure, or else completely abandoning and re-establishing the contact  quickly, which can unbalance the horse. A hand that pulls on a rein to  give an aid has recoil; that is, it continues pulling even as the horse  is giving, until such time as the rider has the presence of mind to  release it, which is usually too late as far as the horse is concerned.  By fixing the hand momentarily, the horse rewards himself instantly when  he gives, and the rider need do nothing but keep still for that moment  and let the horse respond.  The rein becomes almost like a side-rein,  but only for a moment, giving the horse the chance to find the response  the rider wants and reward himself once there. 
 
Another concept of note that can be applied to any discipline of  modern riding is “hand without legs, legs without hand,” and nowhere is  it more applicable than with the Direct Rein of Opposition when used on  both sides. The concept means exactly what it says: when using the leg,  lighten the hand and allow the horse to move freely forward, and when  using the rein, release the legs and allow the horse to come back  without resistance or clashing of the aids – then alternate between the  two for the desired effect. Neither effect is sustained indefinitely,  but is a series of small corrections and adjustments taken in turn, as  needed, with alternate releases of pressure. It seems a simple enough,  common sense approach, and yet dressage books and equitation manuals are  filled with the language of “driving the horse onto the bit,” “riding  the horse into the hand,” and “pounds of pressure in the hand,” etc. I  imagine the balance between restraining hand and driving leg aids as  being like juggling a ball back and forth – one would not hold onto it  with both hands and pull it back and forth, but must release it; a light  horse is the ball, always somewhere between the driving and restraining  aids, never on them both at once. 
Uses:
- Single Rein: when used unilaterally, this rein can be useful for collecting on the outside rein, preparing the canter departure to help horse balance on the outside hind and free the inside lead, in a turn on forehand, as a brief restraining aid like a one-handed half-halt, etc.. This rein can be used for a turn on the forehand, due to its tendency to displace the quarters outward, but this is the only turn it should be used to make. 
- Two Reins: when used bilaterally, this rein will produce a halt or rein back, and with proper timing of alternating pulses, closing the fingers and resisting momentarily, this rein effect can help shorten a horse's base of support and produce collection, provided the necessary engagement and impulsion are there. 
Faults:
The  most common fault committed with this rein is to use it in turning,  circling or bending.  Other faults include pulling backward on the  rein(s), exerting a steady force or pull (i.e., not using a fixed hand,)  and not giving the horse a proper release.  Of course, as this is the  stopping rein aid, there are times when pulling may become necessary, as  when a horse is running away with the rider; however, pulling should be  the exception and not the norm with this, or any, rein aid. 
Compatible Reins:
As already discussed above, this rein is compatible with itself, i.e., it may be used simultaneously on both sides of the horse without conflict. The other rein it may be used with is the Indirect Rein of Opposition Behind the Wither, which is to be the subject of the next post.
The Five Rein Aids:
The Indirect Rein of Opposition in Front of the Wither
The Indirect Rein of Opposition Behind the Wither
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In Practice:
What it means to be “On the Bit”
On the Bit: Calm, Forward, and Straight
Open Letter to Practical Horseman (On The Pulley Rein)
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Over Fences:
The Crest Release and How it Ruined American Jumping
