Neither. M,TUES,...TH, F. I used to go 1 on 1 off though. Sometimes 2 on 2 off. It works well enough. I am of the opinion though that you need to space your time between workout to at least 7 days(especially if you go heavy), so I had to adjust the routines a tad to comply with training eod. Still though, it was nice to go into the gym thinking "get this workout good, and you'll have a nice day off tomorrow".