How many reps to build muscle or get stronger?

You've probably heard that 1 to 5 reps builds strength, 8 to 12 builds muscle and 15+ builds endurance. It's not wrong, but it's tidier than reality. The number of reps matters less than how close to failure you take each set.

What the research says

A 2017 meta-analysis by Schoenfeld, Grgic, Ogborn and Krieger compared heavy and light loads. When sets were taken close to failure, muscle growth was about the same anywhere from roughly 6 to 30 reps. Strength, though, improved more with heavier loads, because lifting heavy is a skill you get better at by practising it.

A practical guide

• 1 to 5 reps: best for getting stronger on a specific lift. Use it on big compound lifts like squats, deadlifts and the bench press.
• 6 to 12 reps: the most time-efficient for muscle. Heavy enough to build strength too, light enough to do plenty of sets.
• 12 to 20+ reps: good for small muscles and joint-friendly exercises: lateral raises, curls, face pulls, calf raises.

Effort is the real target

A set of 12 where you could have done 25 does very little. A set of 12 where you had one or two reps left in the tank does a lot. That's why effort targets, measured as reps in reserve, matter more than the number on the page. Aim to finish most work sets with 1 to 3 reps left.

Match reps to the exercise

• Heavy barbell lifts: lower reps keep your form solid. Fatigue breaks technique on a 20-rep squat long before the muscles give out.
• Machines and cables: higher reps are safe and effective, since balance isn't the limit.
• Dumbbells: the jumps between sizes are big, so use a rep range and add reps before you go up a size.
• Bodyweight: you can't add weight, so use reps and harder variations. See strength training with no equipment.

Tip: Use a mix. Heavy work on your main lift of the day, moderate reps on the next two, higher reps to finish.

How Liftsmith picks reps

Liftsmith gives each exercise a rep range that suits it: lower for heavy compounds, higher for small muscles and machines. Each set has an effort target for that week of your block, and when you beat the top of the range it adds weight next time. The reason is shown under every target, so you always know why it asked for that number.