If you’ve achieved a measure of control of both ends of your horse while practicing leg yield in hand, you should find shoulder in fairly simple, as it is a logical progression for your horse.
Reasons to teach shoulder in
- Where leg yield is largely about crossing the legs to stretch and mobilise the lower back, shoulder in is more about getting your horse to carry weight on his inside hind leg
- One of the main benefits to shoulder in, is that you are only asking your horse to bear weight on one leg at a time
- Because of the position your horse is going to be in when shoulder in is correctly achieved, his inside hind leg will be directly beneath his body weight. Provided you don’t let him rush, this will result in him bending the hind leg joints more acutely and lowering his croup as a result
- Shoulder in is primarily a strengthening exercise
- Further implications are that once you also achieve this movement under saddle (which is easier for him to understand ridden once you have introduced it in hand) it also becomes one of your major straightening tools