Scientists aren't sure if the temporary muscle puffiness you get after working out is a good sign that your muscles will actually grow bigger over time. It might work for some muscle groups but not others, so we need more studies to figure this out.

When you lift weights and your muscles get bigger temporarily (that's called the 'pump'), that doesn't actually tell you if your muscles will grow bigger for real over time. Scientists found that muscles that swell a lot right after exercise don't always end up growing the most.

Your muscles can actually swell up bigger right after just one workout than they do after training consistently for several weeks.

If a guy new to lifting weights gets a bigger muscle swell right after his first workout, he’s likely to gain more muscle over the next 6 weeks.

When you lift weights for a long time, some muscles like your chest can grow bigger than they do right after a workout, but this doesn't happen with your arm muscles like biceps.

Just because your muscles feel swollen and pumped after a workout doesn't mean they're going to get bigger over time—studies show that even if some people get way more pumped than others, they all end up with about the same muscle growth in the long run.