I grew up swinging axes, sledgehammers, carrying five gallon pails of water for long distances, pushing and pulling round bales, throwing square bales, shovelling wet & heavy shit, chasing and manhandling cows, moving random heavy shit, fixing machinery, and much more.
Not only was I strong, I was in good shape. I see these strength and conditioning gyms / gurus doing their own version of my childhood chores. Not to mention the high quality of food I had access to. Garden vegetables, beef, pork, eggs, milk, chicken, potatoes.
Now I understand that muscular imbalances are an issue, combine that base with 2-3 days a week at a gym.