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 already fit and lift weights, doing way more sets (15–20 per muscle group per week) doesn't make you stronger faster—in fact, you might even gain less strength than if you stick to just 5–10 sets.

If you're already fit and lift weights, doing 5 to 10 sets per muscle group each week will make you stronger—but doing more than that (like 15 to 20 sets) won't make you any stronger, no matter how hard you push.

If you lift weights the same total amount each week, it doesn’t matter if you do it in one big session or split into three smaller ones—you’ll get just as strong and build just as much muscle.

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.