He gets transported into the game and has to survive in the village because of reasons
He did start to work out a little thanks to the logs he gets sent to him, but while he does have some arm and leg muscle he has no stamina and is hardly THAT well trained.
he's ripped because it's shown in early chapter, he got into muscle training since that stabbing incident. And considering he's been hikki for years, well apparently that's the result...