People who already train regularly are more likely to see real muscle growth when their workout plan is customized for them, rather than using a one-size-fits-all routine — and the difference is about half as many more people seeing real gains.

If you're already experienced with weight training, doing the exact number of sets your past logs suggest (1.2 times your usual) builds more muscle than doing a fixed number of 22 sets every week — and this is shown by measuring your thigh muscle thickness with ultrasound.

Changing up your workout routine all the time—like switching exercises every week—won’t make your muscles grow bigger than sticking to the same routine, even if you do more total work in the varied version.

Doing more sets of weightlifting seems to build muscle more reliably than how close you get to failing on each set—whether you stop short or push to exhaustion doesn’t change the muscle growth much if you’re doing the same number of sets.

Doing your workouts more often per week doesn’t seem to help you build more muscle, as long as the total amount of lifting stays the same.

A lot of workout studies don’t have enough participants to notice small but real muscle gains in people who already lift weights, so their results might be confusing or wrong.