Or take a blacksmith. He is constantly using or exercising his arms. So you'll find them as hard as nails.
While his legs—because he doesn't use them so much—aren't likely to be nearly so well developed.
A man in an office or store usually has soft, flabby, weak muscles.
But let that man take up some form of exercise, like tennis or base ball, and his muscles will soon be strong.
It is a law of Nature that our minds and muscles grow by proper use, building themselves up to meet any demands made on them.
That is why, after any sickness which leaves the body weak, doctors nearly always tell you to take plenty of exercise.
Until recent years, the only way to develop strength was by active exercise; movement of the muscles by their own force, as in walking, chopping wood or playing some game.
But nowadays there is a substitute for exercise.
Massage Is a Substitute For Exercise
Called Massage; a sort of artificial exercise; a way to strengthen muscles without using them.