A. V. Bock

Studies in muscular activity

THE object of this paper is to report a study of the physiological state of four normal male subjects during exercise on a stationary bicycle. In the interpretation of the data obtained consideration has been given to the character and severity of the work done by a given subject. An analysis of the results appears to show some of the adaptations which the organism as a whole may make as a result of physical training. The variations found in the different subjects are sufficiently great to ilidicate the range of individual reactions to the same type of muscular exercise, and for this reason throw some light on observations made in the past by others in which apparently contradictory results have been reported. All of the subjects of this study were known to be in good health. One subject, DeMar, the Marathon runner, has maintained a state of physical training continuously for approximately 20 years. This athlete runs ten miles or more daily with few exceptions throughout the year. The subject C.V.C. had never had extended experience in any form of physical exercise. Both D.B.D. and A.V.B. have led sedentary lives but have been accustomed at times to periods of hard physical work. The former was a runner while in college. The study made in the case of DeMar covered a period of two weeks, the experiments being done before breakfast. The data in the case of C.V.C. were collected in a period of about six weeks, those on D.B.D. and A.V.B. in six months, the experiments generally being done 1-3 hours after breakfast.

On the partial pressures of oxygen and carbon dioxide in arterial blood and alveolar air

EVER since the work of Haldane and Priestley(l) (1905) on the pressure of C02 in alveolar air, and that of Krogh(2) (1910) on the mechanism of gas exchange in the lung, it has been generally believed that the partial pressure of C02 is the same (to a close approximation) in arterial blood and alveolar air. The relation, however, of the partial pressure of oxygen in alveolar air to that in the arterial blood has not been determined with the same accuracy. This uncertainty is due in part to the dispute concerning the role played by the lungs in oxygen transfer, in part to difference of opinion regarding the mechanics of pulmonary ventilation, and also to lack of precise knowledge of the facts. It is the purpose of this paper to present data with reference to gas exchange in the lung. Our experiments have been performed on normal men while they were breathing air or low oxygen mixtures.

Studies in muscular activity: IV. The "steady state" and the respiratory quotient during work.

IN view of the present conflict of observations and opinions concerning the respiratory quotient during work, the subject of this paper is approached by the authors with some trepidation. Questions pertaining to basal or non-basal conditions, duration, character and intensity of the work period, nature of the diet, experimental procedures, and the existence of a steady state have all been raised in connection with the interpretation of the respiratory quotient. In the preceding papers of this series some account has been given of methods and of experiments conducted during work on a stationary bicycle. It is proposed now to examine in detail experiments demonstrating a steady state, the condition in which, for the most part, our work has been done. In addition we present data concerning the respiratory quotient in a series of experiments in which this quantity has been determined at intervals up to one hour or more from the beginning of work. Some of these data have been dealt with in the preceding paper. The significance of the R.Q. is discussed in the light of the data given.

Studies in muscular activity: I. Determination of the rate of circulation of blood in man at work.

THE circulation rate in man may now be determined by three methods: the nitrous oxide method of Krogh and Lindhard(), the ethyl iodide method of Henderson and Haggard(2) and the type of method first used by Christiansen, Douglas and Haldane(3). This Haldane method, so-called, has proved most satisfactory in our hands. Three years ago Field, Bock, Gildea and Lathrop(4) described two modifications of it and reported a series of determinations on normal resting subjects. They demonstrated the relationship between the carbon dioxide pressure of arterial blood and that of Haldane-Priestley samples and thus helped to establish the trustworthiness of this method. Since that time the application of the Haldane method to exercising subjects has been under investigation in this laboratory. The method finally arrived at has involved experimental studies, at various metabolic levels, of the slope of the carbon dioxide dissociation curve of oxygenated blood for each subject; of the relation between the carbon dioxide pressure of arterial blood and that of alveolar air; and of methods for determining the carbon dioxide pressure of oxygenated venous blood. The first of these problems has presented no great difficulty. It has been discussed to some extent already by Bock and his associates (5) and will be discussed more in detail in later papers of this series. It is enough to say here that up to a given metabolic level, fairly well defined for each individual, the carbon dioxide curve is unappreciably changed in height and slope. Beyond this metabolic level the height of the curve falls off rapidly and its slope changes slightly. On each subject studied during exercise samples of blood have been drawn at each of several metabolic levels and employed for orienting the carbon dioxide dissociation curves. The technique for collecting during exercise samples of alveolar air which have the same carbon dioxide pressure as that of arterial blood has been described by Dill, Lawrence, Hurxthal and Bock(6). It was