"Exercise is as much of a vital necessity for man as air, water and food, in the sense that no man who does not take exercise regularly, can be perfectly healthy. By “exercise” we do not mean merely walking, or games like hockey, football, and cricket; we include under the term all physical and mental activity. Exercise, even as food, is as essential to the mind as to the body. The mind is much weakened by want of exercise as the body, and a feeble mind is, indeed, a form of disease. An athlete, for instance, who is an expert in wrestling, cannot be regarded as a really healthy man, unless his mind is equally efficient. As already explained, “a sound mind in a sound body” alone constitutes true health. (Chapter VII, Exercise)"