When you do compound exercises like dumbbell rows that work multiple muscles at once, they might build muscle in some parts of your arm about the same as isolation exercises like dumbbell curls that focus on just one muscle. But in other parts of your arm, the two types of exercises might build muscle differently.

The study compared dumbbell rows vs curls and found curls actually built more muscle overall (11% vs 5%), which goes against the claim that they produce similar results. Also, the study didn't look at specific parts of the muscle like the 25% or 75% regions mentioned in the claim.

The study looked at overall muscle thickness, not specific regions like the 25% and 75% areas mentioned in the claim. It found that isolation exercises (curls) actually built more muscle than compound exercises (rows), which contradicts the claim that they can produce similar results in some areas.