Lifting heavy weights with fewer reps and longer breaks makes your arms stronger and bigger faster than doing more reps with lighter weights and shorter breaks, especially for guys who already work out.

Lifting heavy weights with fewer reps and longer breaks builds more muscle and strength than lifting lighter weights with more reps and shorter breaks in men who already work out.

Lifting lighter weights many times in a row helps well-trained young men do more push-ups longer than lifting heavier weights fewer times, after 8 weeks of training.

Lifting heavy weights with longer breaks between sets makes young men stronger faster than lifting lighter weights with shorter breaks, based on an 8-week study.

Lifting very heavy weights a few times with long breaks builds more muscle and strength faster than lifting lighter weights many times with short breaks, when the total amount of lifting isn't the same.

If you're already strong and lift weights regularly, doing 10–15 hard sets per muscle group each week for 2 months will make you stronger and add a little muscle — whether you train your whole body every day or just once a week.