Analysis of medieval knights’ skeletons shows that the bones of their sword arms and shoulders are much thicker & heavier than the other, probably due to the extensive training.
This facet of arms training for the period of time may also have led to the myth of Richard the III's so-called "hunchback". The greater muscle and bone build-up on his right side, according to this theory, gave him the one-sided built-up appearance that was eventually propagandized by old Will Shakespeare (who, after all, knew which side of the Tudor bread his butter was on) in his play.