When the total amount of work done for the biceps and triceps is the same, doing one exercise per muscle group produces the same muscle growth as doing multiple exercises over eight weeks.

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

Multi-joint exercises that engage both the biceps and triceps add a significant amount to the overall workload these muscles experience during a workout.

Whether you lift your arm weights slowly or with a little swing, your biceps and triceps both get noticeably bigger after eight weeks of training—your triceps grow even more than your biceps.

If you're a young guy who already lifts weights, doing twice or three times as many sets per week won't noticeably grow your biceps more over six weeks — even if there's a small trend toward more growth.

If young men who have never weight trained before do bicep curls twice a week for 10 weeks, their arm strength increases by about 12% on average.