Many factors go into this, but the CDC says you’ll get the most health benefits from strength training when you do reps to the point where it’s hard to do another without help. The CDC recommends starting with eight to 12 reps per activity, aiming to do those sets two or three times. By the way, this doesn’t just mean lifting weights—strength training can also include working with resistance bands, doing push-ups and sit-ups, and doing some forms of yoga.