Lifting lighter weights can build just as much muscle as lifting heavy weights in beginners over 12 weeks, even if you do fewer total reps.

If a young, healthy man lifts weights for 8 weeks, his muscles will likely get bigger—by about 6%, give or take a little.

Lifting weights with fewer reps (3-11) builds more muscle than doing lots of reps (20-28) in young guys new to training, especially after 8 weeks.

When untrained young men lift weights until they can't anymore three times a week for six weeks, and they do the same total amount of work, their muscles grow about the same amount whether they lift heavy or light weights.

If you're already fit and lift weights, doing 5 to 20 sets of exercises for each muscle group every week won't make you grow bigger muscles any more or less than any other number in that range.

Eight weeks of moderate-intensity weight training increases muscle thickness in the chest, biceps, and thigh muscles by 5–10% in men who have not trained before, even if they do not train to muscle failure in every set.