For men who already lift weights, doing either high-intensity or high-volume workouts for 8 weeks didn't make a big difference in leg strength or muscle size.

Even if you’re already strong—squatting almost twice your body weight—adding more sets will make you stronger, but won’t make your muscles grow more than doing a moderate amount.

If you're already strong and lift weights, training each muscle group either once or five times a week for eight weeks will give you about the same strength gains on the bench press, squat, and row.

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.

Lifting heavier weights for fewer reps makes your legs much stronger than lifting lighter weights for more reps, but both types of training help your upper body a little bit too, and this might work differently for different muscles.

Whether you rest 1 minute or 2.5 minutes between sets, your strength gains in squat and bench press end up being about the same after 10 weeks of training.