Straight from our told-you-so file: Scientists in Japan found that men built more muscle by doing 3 sets of 10 dumbbell curls than by doing just 1 set. What makes the study unique? Twice a week, the lifters did the 3-set routine with one arm and the 1-set routine with the other.  So genetic differences among lifters weren’t a factor.  Here’s how much those 2 extra sets helped.

• Muscle gain with 1 set 8% with 3 sets 13%
• Strength gain with 1 set 20% with 3 sets 32%

From Men’s Health July/August 2011