While I totally agree with both posts so far, I do think that I would put a slightly different spin on it. When riding an English discipline, the horse should be at the end of whatever length of rein the horse is given, so that if the rider opens his/her hands, the slight tension that the horse puts on the bit should gently slide the reins through the rider’s hands, until the rider increases the finger and hand tension so that the horse can no longer easily slide the reins through the rider’s hands. The horse should then stay with head position until the rider gently shortens the reins to bring the horses head up, at which point a horse that has been taught to stay at the end of whatever rein length he/she is given, will follow the bit back up. This is not necessarily true for the Western disciplines, as correct western riding has a slight loop in the reins rather than a straight rein from the rider’s hands to the horse’s mouth, with the horse creating this slight tension by always staying at the end of the rein length. A horse that has been taught to stay at the end of whatever rein length he is given is not necessarily setting himself up for
a buck, because the neck muscles should be relaxed and stretching, while for the buck the horse has to be tensing (which shortens the muscles) as it is the tensed muscles that produce the buck. A horse who is jerking on the reins is not putting “light” tension on to stay at the end of the given rein length. The means that the rider has to know his/her horse and be very aware of what the horse is doing & thinking at the end of the reins. Just as the horse can learn to feel minute changes in tension in the rider’s body, the rider can learn to feel and interpret minor changes in the horse’s body, but it takes a lot of hard work and practice on the part of both the horse and rider to develop these 2 mirror image skills. This is not an overnight, or even a “30-day” fix, but most riders who achieve this have no doubt that it is worth the effort.