Tl;Dr modern training methods based on periodicity and what the body can handle are at most what? 60 -100 years old? Sports science and physiology isn't that much older?
Plus the selection profile of people competing in these sports is getting broader.
Latter I reckon. ie. at what stage of human history did Kenyan runners actually get the ability to compete on the world stage? They didn't just suddenly become great distance runners but they did quite rapidly get the opportunity to travel overseas and make money from being great distance runners.
Tl;Dr modern training methods based on periodicity and what the body can handle are at most what? 60 -100 years old? Sports science and physiology isn't that much older?
Plus the selection profile of people competing in these sports is getting broader.
I dunno.