"Some trainers recommend to their pupils for the training of all muscle groups one and the same (light) weight and believe they are able to obtain the same effect by frequent repetitions. My experience has taught me that this is wrong, for the muscles of men or animals who are distinguished for certain feats of endurance are by no means over-developed. A long-distance runner or long-distance cyclist always has comparatively thin legs, as have a racehorse, stag, or greyhound. Nature does not act without aim and purpose. Hence there is a great difference between feats of endurance and feats of strength. One must consider that, although it is quite possible to enlarge muscles by certain light, prolonged exercises, at the same time the development of the sinews may be neglected, and it is the sinews which transport the action of the muscles to the bone xframe. The sinews can only be exercised and strengthened by correspondingly heavy muscle work. Besides, to take a paradoxical example, it is quite impossible to improve strong muscle groups, as, for instance, the hip muscles, with light-weight exercises. A further illustration of the fallacy of attempting to develop the muscles by frequent repetitions with the same light exercises may be found in a comparison with any and every other form of athletics, in which a man would never think of merely repeating his training programme. In order to improve himself either in pace or distance, he must set himself a steady progression of arduous effort". - George Hackenschmidt This is an original version, restored and re-formatted edition of Hackenschmidt's 1908 classic.