When people do different types of weight exercises - ones that move just one joint (like bicep curls) versus ones that move multiple joints (like squats) - the results for building muscle and strength might be different for people who already workout regularly compared to people who don't exercise much.

If you're a guy new to lifting and you start your workout with big compound moves like the bench press instead of isolation exercises, your chest muscles grow more—probably because you're not too tired when you do the main exercise.

For beginners, it doesn't really matter whether you do exercises that work one joint (like bicep curls) or multiple joints (like squats) - what matters is what equipment you have, what movements feel natural, what you enjoy, and how much time you have. The muscles will grow about the same either way.

When young men who haven't trained before do either multi-joint exercises (like curls) or single-joint exercises (like bicep curls) for 10 weeks, their arm muscles grow by about the same amount - there's no meaningful difference between the two types of workouts.

Doing extra arm isolation exercises like bicep curls and triceps extensions doesn't help you get stronger or build more arm muscle than just doing big compound moves like bench presses and pull-downs — at least not for beginners after 10 weeks.

If young men who haven't exercised before do either multi-joint exercises (like pull-ups) or single-joint exercises (like bicep curls) for 10 weeks, their arm strength increases by about the same amount - neither type of exercise is clearly better than the other.