The number of men who "keep fit" in this country has been surprisingly few, while the number of those who have made good resolutions about keeping fit is astonishingly large. Reflection upon this fact has convinced the writer that the reason for this state of affairs lies partly in our inability to visualize the conditions and our failure to impress upon all men the necessity of physical exercise. Still more, however, does it rest upon our failure to make a scientific study of reducing all the variety of proposals to some standard of exceeding simplicity. Present systems have not produced results, no matter what the reason. Hence this book with its review of the situation and its final practical conclusions.