If young guys lift weights in a structured way for 10 weeks, eat about 1.8 grams of protein per kilo of body weight every day, and have supervision, they can get way stronger—adding around 80–85 kg to their leg press and 11–12 kg to their bench press max lifts.

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 female college athletes who already lift weights add a specific workout plan and eat 24 grams of protein before and after each session, they’ll get way stronger in their legs—adding about 90 kg to their leg press max in just eight weeks.

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.

Older guys between 60 and 75 who aren't very active can get a lot stronger in just 12 weeks by lifting weights twice a week—even if they don’t take extra protein right after workouts or before bed, as long as they’re already eating enough protein overall.

If young guys lift weights for 12 weeks, their muscle strength gains in the leg press don’t seem to be linked to how much their hormones spike right after each workout.