Years ago "professional" sports being Aussie Rules, Rugby, cricket whatever were not really "professional" the money just wasn't there, so yeah they trained hard a couple of times a week, but also the majority also worked for a living they had to just to get by.
These days they get payed big dollars to perform and in most cases play winter and summer sports all year round, train 5 - 7 days a week an much more finely tuned, as already pointed out just look at body shapes of sportsman these days compared to 30 - 40 yrs ago, I would almost argue that todays amateur parks footy players at some higher levels train harder then the "professionals" of 30 - 40yrs ago.