Explore "Daily Training" by E.F. Benson on Textopian. Read with annotations and highlights.
It will not in this chapter be necessary to go at all deeply into the physiological effects and changes wrought in the body by exercise, but at the same time for those interested in the subject it will be well to sketch in the merest outline the general effect of exercise, and give the reasons why (a rule so universal as to be considered as practically without exception) those who take exercise, especially when they take it in air, where there is a sufficiency of oxygen, are in better health than those who do not.
Now every organ in the body is either in itself a muscle or a system of muscles, or is controlled by muscles. That is to say, none of the infinite processes incidental not only to any movement, but to even perfectly passive life, are independent of muscular action, automatic it may be, and unconscious or sub-conscious, but still muscular.