Doing isolation exercises before compound lifts (like leg extensions before squats) doesn’t make you stronger or change your body more than doing the lifts in a different order, as long as you’re already trained.

Doing single-muscle exercises first makes you tired, so you can build muscle with lighter weights on bigger exercises.

Starting your workout with big lifts like squats and bench presses doesn’t make you stronger or change your body differently than starting with small lifts like leg extensions — as long as you train hard for 12 weeks.

When you tire out a muscle with one exercise before doing a bigger workout, you can't do as many reps in the big workout, so you end up doing less overall exercise than if you just did the big workout alone.

Doing all your sets for one exercise before switching to the next might build a tiny bit more muscle than mixing exercises up, but it's such a small difference we can't be sure it's real.

Doing a simple exercise right before a harder one with no break doesn't make you stronger or build more muscle better than just doing regular workouts, according to current research.