When comparing strength gains from multi-joint and single-joint exercises, differences in the number of repetitions used may influence the results, because training with fewer repetitions is more similar to how 1RM strength is measured.

Lifting weights with one joint (like leg extensions) transfers better to holding a static position than complex lifts like squats, because it’s easier for your body to use the same muscle pattern in both cases.

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.

Lifting heavy weights for just a few reps makes you stronger in exercises that work one muscle at a time, more than lifting lighter weights for many reps, especially if you already work out regularly.