How can you teach a horse to be more reactive to the aids?

Train your horse to go forward from your leg and to slow down from the reins and seat

The principle of action is reaction. Horses naturally yield away from pressure. It is very helpful to teach the horse to move away from pressure, like in the washing place when you ask the horse to step aside. For example, when you place your hand on the hindquarters (action) and the horse steps aside to make room for you (reaction), releasing the pressure is the reward for the horse when he gives the right reaction.

This works the same when you are riding. You want the horse to go forward (reaction) away from the pressure of your leg (action). You also want the horse to slow down (reaction) when you put pressure on the reins or seat (action). By consistentlytraining your horse to go forward from your leg and to slow down from the reins and seat, the understanding between horse and rider increases because the horse always knows what he is supposed to do. You can’t expect the horse to understand this principle right away, so in the beginning be satisfied when your horse goes forward from the pressure of your leg and slows down when you create pressure on the reins. Further along in the training, you want the horse to maintain his own balance, rhythm and acceptance of the bridle. In this phase of the training, it is important that the horse develops self-carriage without your consistent support of hand and leg aids.