If you do something enough, it’ll give you muscles even if it isn’t hard to do it once. Sure, you won’t get big and buff, but you will train your muscles- not everyone works out to get huge, many just want to feel physically better in their bodies. Just look at people who swim or dance as their only sport, or even those who do ‘light’ manual labour such as gardening. They look more muscular than those who don’t engage their muscles much at all.