Say I have two different exercises in my routine, E1 and E2. Is there a difference in outcome between doing E1-E1-E1-E2-E2-E2 and E1-E2-E1-E2-E1-E2? As it's common with this type of questions, I've read many answers but they're either based on anecdotal evidence or just opinions. Has anyone heard of any serious, evidence based study made about this?
I do not remember which papers or research I got my knowledge on these from but here are what I remember and make sense to me!
E1-E2-E1-E2 sounds like a superset, unless you mean you perform E1, rest, then E2, then rest, so on and so forth. If that’s the case, I wouldn’t think there is much difference UNLESS you have a specific goal/movement you want to achieve. For example, if I want to hit my squats hard and go “heavy”, I’ll do all my squat sets first (E1-E1-E1-E2-E2-E2) as I’ll be feeling fresh and my body is at its maximum energy level (glycogen).
Alternate E1 and E2 like a superset if I want to save time and E1 and E2 recruits different prime movers (biceps and triceps). If there is no rest between E1 and E2 and they both recruit the SIMILAR muscle fibres (shoulder press and shoulder lateral raise), I don’t think it is beneficial as motor unit recruitment may decline due to central nervous system fatigue. If your goal is muscular hypertrophy, mechanical tension is important.
You can explore articles by Chris Beardsley. He’s awesome. https://medium.com/@SandCResearch/why-does-central-nervous-system-cns-fatigue-happen-during-strength-training-e0af3f5e4989
Bottom line, I always believe it depends on your goal, what equipment you have and the time you have.