to zigzag or not to zigzag

[Scott Stevenson]

BG,

If you're doing TIER I, you're only doing 1 set of squats.

I'd simply at yet another warm-up using squats before your first working sets for that exercise. Warming up is doing whatever it takes to warm up, so simply do that.

Zig-zagging is a form or pre-fatiguing and/or adding more focused stimulus and volume to a give muscle group without taxing the nervous system as much doing compound exercises would. You get variety of stimulus, focused (isolation exercise) and/or pre fatiguing depending on how you order the exercises.

-S