Interesting Question

Hi,
 
I've tried a few routines... mainly HIIT, 3 day full body, 3 day split, 4 day split, and similar variations.
 
There are pros and cons of each and whether you chose to do one or the other the thing everyone seems to agree on is that you need to constantly change your routine to "shock" your body into growing.    However, one thing I also hear a lot is you should consider changing routine every 4 - 8 weeks.  
 
My question is....If changing your routine is so good, would it not be better then to constantly be changing your routine?  I.e. HiiT for a week, followed by a Push, Pull, Legs week, then a 3 x a week full body workout.  
 
You could even change the routine every session. I.e. Monday HIIT, Wednesday Legs, Friday Full Body, Monday Push, Wednesday Hiit, Friday Pull etc.
 
That way your body never gets the time to adjust and is always being shocked.  I am no expert though so maybe you guys explain why this won't work but any advice/criticism is very welcome.
 
Thanks.

sticking with one routine allows you to see progress, dfifferent rep ranges and splits amy work better so lets you test them out over a period of time.

Also if you changed every session then youd soon get used to doing that.

Chaning youre rotuien is only neccesary when youre plateuing, and not always then just a slight tweek may help.