I have been enjoying the Westside routine the past month or so. I am eating to gain mass, and it's the old adage....I hit the weights 3x a week, but am looking to chuck in a cardio session also.

I wouldn't want to try HIIT prior to my Leg day, which is Wednesday, so the ideal place would be Thursday. Friday is an upper-body based day, so I don't need my legs (as such!). Other than the first couple of weeks after a rest, I do not do too bad with DOMS, so I think I could managed HIIT on my stationery bike on Thursday.

Would it be a good idea to chuck it in there, or should I rest up on the Thurs?