I am no expert, just a guy reading the Internet. And it seems like there are two opposing factors. The increased access to nutritious food has dramatically increased health, shown in the increased average height. The exception to this is the first 50 years, 1830-1880 when widespread dietary deprivation and severe inequality caused a decrease in height (take this as a warning I guess).

The other factor is that we all get significantly less physical activity than before, and obesity is a increasing problem.

And while the first effect is a effect of the machines, it is the latter effect I think most easily maps onto today's situation.

Personally I am quite certain that if you could teleport 100 random 20-year old from 1820 they would be better than 100 random 20-year old today at most physical tests, especially if you gave them food first.

Considering developed societies with access to those specialized diets and medical science, the median person is definitely not stronger than the median person from a pre-industrial society, even taking malnutrition and injury into account. It seems you've never tried to arm-wrestle a farmer before.

But what about average person, not a professional athlete? In past people suffered from malnourishment, but today they suffer from obesity.

We also know that testosterone levels (which are connected with muscle mass, recovery etc.) are lower today than even few decades back.