In conjunction with my book, for even FASTER healing I STRONGLY suggest you implement Dr Adam Story's stretches as shown in his videos below. He has many others which I strongly recommend, I have done many of his knee ones in particular and found them tremendous.

These are the ones I have found for the back. You will be able to find all his videos on YouTube.

THESE ARE THE LINKS HE MENTIONS IN THE ABOVE VIDEO: The stretch:

https://www.youtube.com/watch?v=AATJe...

The strength exercise: https://www.youtube.com/watch?v=Cbvbp...

How to tell you have piriformis syndrome: https://www.youtube.com/watch?v=kvPJD...