There are riding instructors who start every lesson by explicitly asking their students to take up the reins and then plan the rest of the session based on this first impression. When a horse eagerly walks forward on long reins and shows rhythmic long strides, establishing contact with the reins must not change these qualities of motion in any way.
If you make the effort to concentrate on this ordinary task, you will realize that it is anything but simple. Here is an exercise to improve your feel in this area: Start walking on a long rein and focus on your seat and on feeling the good quality of the walk. There should not be any change in the walk’s quality as you take up the reins. There are quite a number of horses that develop negative tension the moment contact gets established, and the good walk they were showing before becomes tense, less eager, and irregular. If you take your time and focus on this process right from the start and every time you take up the reins, you will experience fewer problems with the walk later on in your riding career.
In advanced dressage tests, you receive double the amount of points for walk because it is regarded as one of the touchstones of correct classical riding. The end of this movement is where the rider takes up the reins again. If done successfully it proves that you have trained your horse correctly and are a sensitive rider. Investing time and patience in this exercise always pays off in the end!