system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: I've heard a bunch of gym goers talk about muscle memory, and how if you were in shape before then its easier to get back in shape because of muscle memory. What can some experts tell me about this?

Like if I could bench press 315 a couple years ago but haven't lifted since, would it be like the amusement park fast pass to where I could hit those numbers again, quicker than someone that  never hit those numbers before? Or even like running times, could I hit those numbers because I've done it before, all because of muscle memory?
gpt
scientific answer:  


when we gain muscle, we're making new muscle cells. when we lose it, we don't lose muscle cells but the individual cells get smaller. its then easier to get back to our peak strength because we don't need to make new cells again, just bulk up the ones we have.