If you lift the same total amount of weight each week, it doesn’t matter whether you do it all in one day or spread it out over three or more days—you’ll gain about the same amount of muscle.

If you lift weights more often each week—like 3 or more days instead of just once—you might see a little more muscle growth, but only if you’re not doing the same total amount of lifting in both cases.

If you lift the same total amount of weight each week, it doesn’t matter whether you spread it out over one day or three+ days—you’ll still gain about the same amount of muscle, no matter if you’re experienced or if you’re training your arms or legs.

If you're already fit and lift weights, doing 5 to 20 sets of exercises for each muscle group every week won't make you grow bigger muscles any more or less than any other number in that range.

If you lift weights the same total amount each week, it doesn’t really matter whether you do it in one big session or spread it out over several days—your muscles will grow about the same either way.

The more you lift weights each week, the less extra strength you gain from each additional session—but your muscles keep growing a bit more even when you train a lot, so strength gains fade faster than muscle growth.