A workout routine that includes one compound lift and one isolation exercise for each muscle group, totaling four sets per week taken to complete fatigue, is associated with the greatest amount of...

Including one isolated arm exercise in a workout routine that already includes compound movements leads to only a small increase in muscle size, even if the total amount of exercise is not kept the same.

If you add an isolation exercise for the arms to a compound exercise without keeping the total amount of training the same, the extra muscle growth is very small.

Doing multiple different exercises with higher volume does not lead to noticeably more muscle growth than doing just one exercise four times per week.

Adding more than one isolation exercise for the arm muscles, after doing compound exercises, does not lead to significantly more muscle growth.