Backcrosses is variation on the
normal Cascade pattern where each throw is made behind your back, with the
ball traveling over your shoulder, and caught in front. Despite its overall
simplicity, Backcrosses is difficult to master, often requiring a month or
more of practice to achieve proficiency.
To learn Backcrosses, it is important to first make sure that you can throw a ball behind your back properly. Start with one ball in your dominant hand. Then, bend your arm behind your back and throw the ball, crossing it over your other shoulder and catching it with your non-dominant hand.
Practice this throw on both sides until you can perform it consistently. The next step is to add in a second ball. Start with one ball in each hand. Then, make a normal Cascade throw with your non-dominant hand. Quickly make a behind the back throw with your dominant hand, and then catch the first ball. Catch the second ball with your non-dominant hand.
Again, practice this on both sides until you can do it smoothly and consistently. Now all that's left is to add in the third ball. Start by juggling a normal Cascade, and then make a single behind the back throw. Catch the ball and resume juggling the Cascade.
Practice this integration on both sides. Once you are comfortable with a single throw, try to perform constant behind the back throws on one side, similar to a half-shower.
Once you can run this Backcrosses half-shower on each side, all that's left is to do behind the back throws continuously. It is best to start with just two or three throws in a row at first, and then gradually work your way up to the full Backcrosses. This trick can be hard on your shoulders at first, so make sure to take some breaks during practice.