The minds of thinking men labor too hard. They frequently use their mental powers prodigally; while there is another class whose highest aim in life is physical labor. The latter class do not exercise the mind. Their muscles are exercised, while their brains are robbed of intellectual strength; just as the minds of thinking men are worked while their bodies are robbed of strength and vigor by their neglect to exercise their muscles.... If the intellectual would to some extent share the burden of the laboring class, and thus strengthen the muscles, the laboring class might do less, and devote a portion of their time to mental and moral culture. Those of sedentary and literary habits should take physical exercise, even if they have no need to labor as far as means are concerned. Health should be a sufficient inducement to lead them to unite physical with mental labor. CT 290.1
Moral, intellectual, and physical culture should be combined in order to have well-developed, well-balanced men and women. Some are qualified to exercise great intellectual strength, while others are inclined to love and enjoy physical labor. Both of these classes should seek to improve where they are deficient, that they may present to God their entire being, a living sacrifice, holy and acceptable to Him, which is their reasonable service.... CT 290.2
Those who are content to devote their lives to physical labor, and leave others to do the thinking for them, while they simply carry out what other brains have planned, will have strength of muscle, but feeble intellects. Their influence for good is small in comparison with what it might be if they would use their brains as well as their muscles. This class fall more readily if attacked by disease, because the system is not vitalized by the electrical force of the brain to resist disease. Men who have good physical powers should educate themselves to think as well as to act, and not depend upon others to be brains for them. CT 291.1