Inactive muscle can be awoken shockingly fast. Especially since muscle is mostly water; thenn add in some inflammation from a new lifting riutine and inches can be added overnight. Still there's protein loss, actual contractile, dry tissue loss. Milos claimed Flex once went from tiny and untrained to possible Arnold champ in 3 weeks! But iirc he landed in the hospital that year for kidney failure, again, and couldn't step on stage. No wonder, dangerous to inflate that fast with bad kidneys.