Doing a pullover exercise before a rowing exercise doesn't make your back muscles work harder than if you just did the rowing exercise by itself, at least for people who aren't trained.

When people who don't usually exercise do seated row exercises, their back and arm muscles work harder as they get tired, showing the body recruits more muscle fibers to keep going.

When people who don't exercise regularly get tired out before doing certain workouts, they can't do as many repeats afterward—about 25% fewer.

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 a light warm-up set before lifting heavy weights might help you build more muscle and get stronger, according to some research that tried a similar but different approach.

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.