Celebrated ancient Greek wrestler Milo of Crotona was said to have developed his strength by carrying a calf every day of its life–starting when Milo was around twelve–until it had become a full-grown bull.
His death seems to have been a source of fascination for eighteenth century painters. He was said to have been killed either by a wolf or a lion (the artist Joseph-Benoît Suvée opted for the wolf in the above painting).
There are loads of other stories about the guy, but they may all be the stuff of legend. Still, I’m going to suggest the calf idea to my son as part of his training regimen this summer.