ILLUSTRATIONS. Bicycle ergometer and universal respiration apparatus Fig. 1. Calibration curves showing heat per revolution of ergometer II PAGE Frontispiece. 27 2. Schematic outline of the respiration apparatus 28 3. Tension equalizer and flexible mouthpiece 29 4. Curves showing oxygen consumption per minute with the subject riding 137 5. Curves showing the total heat output per minute and corresponding external 138 6. Curves showing the pulse-rate when the external muscular work was equiv- 153 7. Curves showing the pulse-rate when the external muscular work was equiv- 154 8. Curves showing the pulse-rate when the external muscular work was equiv- 155 9. Curves showing the pulse-rate when the external muscular work was equiv- 156 10. Continuous records of the rectal temperature obtained by thermal element during severe muscular work 158 vii MUSCULAR WORK A METABOLIC STUDY WITH SPECIAL REFERENCE TO THE EFFICIENCY OF THE HUMAN BODY AS A MACHINE BY FRANCIS G. BENEDICT AND EDWARD P. CATHCART PART I. INTRODUCTION. From the days of Count Rumford, who showed that the muscular work of two horses produced sufficient heat to boil water, until the present day, when mechanical efficiency and the study of body-movements in domestic and in manufacturing industries are receiving much attention, the muscular work of the human body, and particularly the efficiency of the body as a machine, have from time to time been experimentally considered. Unfortunately, most of the observations have been of a desultory nature, so that actual knowledge with regard to the extent and character of the chemical processes which are coincidental with muscular movements has but slowly accumulated. This is due primarily to the fact that in but few places are such studies possible. a The practical results of studying body-motions and eliminating the extraneous muscular movements have been strikingly demonstrated on many occasions; likewise, training has been shown to make possible prolonged and sustained effort by athletes; nevertheless these phenomena have either been considered as due in general to the better training-this broad term covering a multitude of operations-or the causes have been entirely disregarded, the majority of individuals being more interested in the practical results than in the causes. It is not, however, a matter of purely physiological interest, since with the present-day emphasis laid upon mechanical efficiency in the factory and in the home, it is a problem of much practical importance to know more exactly the mechanical efficiency of the human body and the best method of attaining the highest degree of efficiency. Our knowledge of training at this date is woefully deficient. Why a course of training should result in greater muscular strength, what changes in the body produce this end, and what is the best method to use for the purpose are at present either entirely unknown or our knowledge is based only upon practical experience. The trainer believes that a certain routine is best adapted to bring his athlete to the highest state of efficiency, and it would be a simple matter to follow this provided any number or even any two trainers agreed upon a particular routine. We have, however, on the one hand, the advocates of a high-protein diet and a meat diet, and on the other the advocates of a low-protein diet and a vegetarian diet, and it must be admitted that both have based their beliefs on arguments of great significance, although the asserted increased endurance of vegetarians rests as yet upon scant and fragmentary evidence. What is needed to place these practical observations upon a scientific basis is a most careful study of the total metabolism, both nitrogenous and gaseous, combining with this, if possible, measurements of the muscular activity and the total energy transformations. a F. B. Gilbreth, Bricklaying system, New York, 1910. 3 |