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.

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.

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 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.

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.

When young men do heavy squat training with different numbers of reps, all rep ranges make their thigh muscles bigger, but higher rep ranges (like 13-15 or 23-25 reps) make their thigh size grow more than lower rep ranges.