If young guys who don’t work out start doing 3 sets of leg exercises instead of 1, they’ll get stronger legs and bigger thigh muscles—41% stronger and 11% more muscle—but their arms and chest won’t see the same extra benefit from doing more sets.

For young guys just starting out at the gym, doing 1 set or 3 sets of each exercise gives about the same strength boost in the upper body after 11 weeks.

For men who don't exercise much, doing regular leg press workouts with three sets at a moderate weight helps reduce overall body fat and thigh fat more than a different workout method, probably because they do more total work.

If you're a new guy to lifting weights, doing 3 sets of leg exercises 3 times a week for almost 3 months will get you way stronger than doing just 1 set — like 41% stronger versus 21%.

If you've never worked out before, lifting weights for 10 weeks can make your muscles stronger and bigger — especially in your legs and arms — while people who don’t train see almost no changes.

Whether you use machines that change resistance as you lift or keep the same weight all the way through, after 20 weeks of training, healthy men gain about the same strength and muscle size either way.