J. H. Talbott

Studies in muscular activity: VI. Response of several individuals to a fixed task.

EXPERIENCE teaches that individuals are not equal in physical ability. From prehistoric times contests in war and in sport have given convincing evidence of this fact. The question as to how one individual can surpass another in capacity and in skill is at least partially susceptible of analysis in the laboratory. This has been demonstrated by Hill and his associates (1), and by many others. There remain, however, many unanswered questions raised by the rearguard runner. Does he fall behind because of inadequate physical endowment or because of insufficient training? His coach may ascribe his failure to his musculature, to his heart, to his wind or to his guts. Since the empirical observations of the runner and his coach certainly have an objective foundation, it has been our aim to seek a basis for these ideas in physiological and physico-chemical facts.

Adaptations of the organism to changes in oxygen pressure.

WITH increasing partial pressures of oxygen, starting with the lowest value compatible with life, the rate of change of working capacity is at first large but, by the time sea-level or its equivalent oxygen concentration is reached, further increments in oxygen pressure are accompanied by much smaller increases in capacity of the body for oxygen transport [see Margaria, 1929]. The quantitative relationship, however, between oxygen partial pressure and metabolic processes is not well defined in the range of barometric pressures extending (in air) from 500 to 1500 mm. Hg. There is little question as to the beneficial effect of oxygen treatment on pneumonia, but it is not certain to what extent the advantage gained is due to better oxygen supply to an overtaxed heart. Still more obscure is the mechanism of benefit (if it exists) of high concentrations of oxygen on pathological conditions which do not necessarily involve the respiration and circulation. In the case of a normal man we have, on the one hand, the statement of Barcroft [1925] that researches are not worth doing much below 14,000 ft., and the conclusion of Margari a that, even without acclimatization, the working capacity at a barometric pressure of 540 mm. is 88-5 p.c. of its value at sea-level. On the other hand, Furusawa, Hill, Long and Lupton [1924] found that a runner can increase his maximum rate of oxygen intake by two-fifths by breathing at sea-level a mixture containing 40 p.c. oxygen. This observation

Studies in muscular activity: VII. Factors limiting the capacity for work

IN a dog the energy reserve consists chiefly of carbohydrate and fat. For their utilization oxygen must be supplied and carbon dioxide eliminated. The maximum over-all efficiency is probably from 20 to 30 p.c., most of the energy appearing as heat. Hence, if a constant body temperature is to be maintained, provision must be made for heat dissipation. The experiments to be described indicate that, by suitably varying the conditions, inadequacy in any one of the three factors, fuel supply, oxygen supply or heat dissipation, may limit the capacity for work. In our experiments these three taken singly, or in combinations, are of primary importance, although factors of secondary importance no doubt exist. Two dogs were trained to run on a motor-driven treadmill. Most of the experiments were carried out on Joe, an immature male of the foxterrier type weighing 13 kg. Additional experiments were carried out on another dog, a mature female of the Irish terrier type and of the same weight. With the exception of a few early experiments the grade 1 was 17-6 p.c. The rates and other experimental conditions will be given in detail below. Observations were made of: (a) heart rate, using a cardiotachometer previously described; (b) rectal temperature either with a thermocouple during exercise or with a clinical thermometer after it; (c) room temperature; (d) blood lactic acid by the method of Friedemann, Cotonio and Schaffer [1927]; (e) blood sugar by the method of Folin and Malmros [1929]; and (f) morphologicalproperties2 of the blood. Notes were made of the dogs behaviour, particularly during the onset of exhaustion. The nomenclature of Campos, Cannon, Lundir

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: 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