How do you handle a young horse that rears during early training and what does it indicate?

A young horse that rears during early training is displaying one of the most dangerous behaviors in horsemanship, and Clinton Anderson's response addresses both the immediate safety concern and the underlying cause that produced it. The immediate safety response to a rear in progress is to lean forward over the horse's neck — never lean back, which raises the horse's center of gravity and makes a higher rear or a flip-over more likely — and to release all rein pressure. Pulling backward with both reins during a rear is one of the most dangerous things a rider can do, because backward rein pressure encourages the horse to go up rather than come down. Releasing the reins and leaning forward removes the stimulus that is most likely causing the horse to rear and reduces the risk of the horse going over backward. In young horses specifically, rearing during early training almost always indicates one of three things: the horse is being asked to go forward but is prevented from doing so by too-tight reins or too much restraint, it has been frightened by something and is using the rear as an expression of the flight response it cannot execute while being ridden, or it has had a previous experience in which rearing was effective in removing pressure. Anderson's prevention is foundational: a young horse with a confirmed forward response from the leg — one that moves forward readily from a light leg aid — rarely rears because the forward response provides an outlet for energy and removes the forward/backward conflict that produces rearing. Ensuring the young horse is forward before it is collected or restrained is the most important preventive measure. For a young horse that has started to rear as an evasion, Anderson recommends immediately putting the horse to work in forward movement the moment the front feet return to the ground — trotting or cantering forward — so that the horse learns that rearing does not remove the demand for forward movement.