If you're a guy who's already been lifting weights, doing fewer reps with heavier weights and longer rests might build more arm muscle over 8 weeks than doing more reps with lighter weights and shorter breaks.

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.

If you're a guy who's already used to lifting weights, doing fewer reps with heavier weights and longer rests might boost your bench press more than doing lots of reps with lighter weights and short breaks — at least over 8 weeks.

If young men lift light weights with very short breaks between sets for 8 weeks, their upper arms grow more than if they lift heavy weights with long breaks—even if they do the same total amount of lifting—because the short breaks create more muscle-burning stress that helps muscles grow bigger.

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.

When men who don't usually exercise do high-intensity weight training for 12 weeks, they lift more total weight overall than if they do low-intensity training, even if they do the same number of workouts and sets.