Apollo loves doing yoga with me before we start our day. This is one of his favorites, and is also the funniest looking of all the stretches.
The tail pull stretches the pelvis region, especially the croup. This is a problem area for a lot of horses and stretching it feels nice.
How to do the tail pullMove your horse's rear end until his back feet are square.
Starting slowly, pull the tail until you've put your full weight into it. The tail should be in line with the slope from top of croup to dock.
Hold for 1 to 2 minutes. Release slowly.
When first training your horse, you may want to only hold this position for half a minute. Be careful to ease into it and watch their reaction, as some horses don't feel mentally comfortable with a person pulling their tail!
You will also want to teach this with someone at the horse's head to keep them from walking off while you're at the tail. After some time, they will learn to stand for it without an assistant, both from repetition and because it feels good.
Once they learn the stretch and enjoy it, they may even lean forward as you pull back, deepening the stretch.
If you are able, work with a trained equine body worker (such as a chiropractor, masseuse, etc) familiar with horse yoga to make sure you are doing this safely and effectively. There are also many videos online to walk you through the process.