If you're a guy who's been lifting weights for a while, doing either 2 or 4 workouts per week for each muscle can boost your strength by about 8–11% in just 8 weeks—as long as you do the same total amount of work overall.

If you're a guy who already lifts weights, doing 4 workouts a week for 8 weeks will make you way stronger—adding about 25 pounds to your squat and 10 pounds to your bench, whether you stick to the same routine or mix it up.

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.

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.

If you're a guy who's been lifting weights for a while, working out each muscle four times a week doesn’t make you stronger than doing it twice a week—as long as you're doing the same total amount of work.

Lifting heavier weights for fewer reps makes well-trained young men stronger faster than lifting lighter weights for more reps, especially in exercises like squats and bench presses.