How do you develop a young horse's ability to work equally well on both reins?

Almost every horse has a naturally stiffer side and a naturally more flexible side, and developing equal suppleness and responsiveness on both reins is one of the ongoing challenges of correct training. A horse that works well to the left but stiffens, falls out through the shoulder, or loses rhythm to the right has a one-sidedness that limits the quality of its training and places uneven physical demands on its body over time. Addressing one-sidedness requires more systematic work on the stiffer side combined with careful attention to the quality of the easier side, rather than simply spending more time going in the stiffer direction and hoping for improvement. On the stiffer rein, the horse needs more preparation — longer warm-up, more gradual introduction of bend, and smaller demands that allow it to succeed — before the same quality of work asked on the easier rein can be expected. Exercises that develop the stiff side include shoulder-fore on the stiff rein, leg yield away from the stiff side, and transitions that ask the horse to engage the inside hindquarter more actively on the rein where it naturally avoids doing so. The flexible side also requires attention because horses that are very flexible in one direction often become over-bent and fall through the outside shoulder, which is a different but equally problematic form of crookedness. Developing equal work on both reins is a process that takes months and sometimes years, and the trainer must regularly assess which rein is more difficult and adjust the training emphasis accordingly throughout the horse's development.