I read Max Contraction Training...
Sheer is no issue if you are truly isometric, but could be an issue when getting into position.
Personally, I thought the approach was rubbish overall...too much detail for a very non-functional result...
That said, if you like it and it works, more power to you.
"You must have a very strong reason for doing an exercise. If you don't, scrap it and move on." -Jim Wendler