Back then I imagine the real problem wasn't the "hardness" and physical demands of the labor, but the risk of physical injury due to poor safety controls/practices that "caused their bodies to break down."

For women especially, hard physical labor, assuming it's done safely, will do more good than harm. It's one of the few effective means to combat osteoporosis, and something folks have to go out of their way to try reintroduce in the form of exercise and gym memberships these days.

I have a construction worker father and stay-at home sedentary mother whose only labor in life was childbirth and light house cleaning. There's no way in hell I'd sign up for her outcomes over his, even including his acute injuries from easily prevented poor worker safety like the nail in the eye or skin cancer from decades of shirtless hard labor.