bigdumbbell,
There is plentiful evidence to suggest that the Farnese Hercules (and several other famous Greek statues) were modelled very, very precisely on actual living models. Seems the Greeks, Egyptians, Persians (along with the Olmecs, Toltecs and Maya across the pond) were secretly working with specialised and exotic concretes even in prehistory. Statues such as the Farnese Hercules were CAST in a mold. The mold having been made in wax using a living model covered from neck to toe. Once set, the statue would then be finalised by a sculptor, and the head would then be made separately.
Hence the famous statue of Emperor Augustus in armour, arms aloft, sported anatomically exact twenty inch calves and a robustly muscular upper body, however his face is thin and adolescent, supported by a chicken like neck.
The Farnese Hercules in particular has been shown (x-rayed) to contain several times the amount of air bubbles as are found in natural marble... add to this the fact that small scars are evident on the knees and elbows of "Hercules", pores are visible on the thighs, the musculature is exact, far exceeding the anatomical knowledge of the day... and to top it all off... "Hercules" has a patch of acne on his upper back (his buttocks were smoothed for aesthetic reasons).
So if it's a cast of a real, living person... why does he seem so massively muscular, so... well, herculean??
Because the sculptor, having been schooled in the minutiae of proportion in accordance with the Greek tradition... simply produced a head that was a little bit (barely noticeable) too small for the body.
Nifty trick eh? (Ask Sergio!)
Cover the head of The Farnese Hercules (or enlarge it) and suddenly the demi-god is almost mortal.
The Luke