How many sets should I do to build muscle?

The short version: two to four sets per exercise, and over the week around 10 hard sets per muscle or more, which research links with more growth. When you're starting out, fewer is enough to get stronger.

Chango works out the sets for every exercise, counts them per muscle over the week and raises the target as you get used to it.

Why count sets per week, not per workout

What makes a muscle grow is the total amount of work it gets over the week. When the weekly amount is the same, it matters little whether you do it in two workouts or four [1]. That's good news: you can fit your training into your week, not the other way round.

That's why Chango plans by the week. It knows how many sets each muscle has had in the last seven days and builds your next workout to fill the gaps.

Why around 10 sets is a good target

A meta-analysis of weekly training volume found that muscles grew more with more weekly sets, and that 10 or more sets per muscle a week worked better than fewer [2]. For strength, more sets helped too, though you don't need many to get stronger at first [3].

Chango uses this research, adjusted for someone building a habit: big muscles like the chest, back and legs start at 8 sets a week, smaller ones like the arms and calves at 5. As you keep reaching your targets, they grow: big muscles up to 12 sets a week and small ones up to 8, into the range research links with more growth.

Why the target grows slowly

Jumping straight to a high volume makes you sore and tired, and that's when workouts get skipped. Research recommends adding volume gradually as your body adapts [4].

So Chango raises a muscle's weekly target by one set when you've reached it three weeks in a row, and eases it back if you've fallen short for three weeks. You don't need to decide when you're ready for more. Chango sees it from your training.

Why helper muscles count too

Many exercises train more than one muscle. A chest press works your chest, but also your triceps and the front of your shoulders. Chango counts those sets partly for the helper muscles, so you don't end up doing extra work for muscles that already got plenty, and you don't miss the ones that didn't.

What you'll notice

You never need to count anything. After every workout, your 3D figure lights up: a muscle glows fully when it has reached its weekly target, and dim spots show what still needs work. In Achievements, each muscle shows its sets against its target for the week, and over a month or a year you see whether you've trained enough, and enough of everything.