Lifting weights at different effort levels all help men get stronger and build bigger muscles after 12 weeks, but using the lightest effort isn't as good as pushing harder.

Lifting weights at different effort levels (from light to heavy) all made muscles bigger and stronger in men over 12 weeks, but the lightest effort wasn't as good as heavier ones.

Lifting heavier weights with proper form was better than lifting lighter weights for building both muscle strength and size in men after 3 months of training.

If you're already fit and lift weights, doing 5 to 10 sets per muscle group each week will make you stronger—but doing more than that (like 15 to 20 sets) won't make you any stronger, no matter how hard you push.

Lifting heavier weights (60-80% of your max) makes you stronger than lifting lighter weights, even if you do the same total amount of work, especially after 12 weeks of training.

If you're already fit and lift weights, doing anywhere from 5 to 20 sets per muscle group each week will make you stronger and build more muscle — and it doesn't matter much which number you pick within that range.