D. B. Dill

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.

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

Properties of the blood of the skate (Raia oscillata).

In the acid range, carbon dioxide pressure has almost no effect on affinity of skates whole blood for oxygen. In the physiological range the effect is appreciable but still only one-half as great as in man. No difference was discerned between the carbon dioxide dissociation curves of oxygenated and of reduced blood. This was partly due to the facts that the hemoglobin concentration is one-fourth as great as in man and that the carbonic acid-combining capacity (when pCO2 = 40 mm.) is less than in man.The effect of temperature on the oxygen dissociation curves is identical with that found by Brown and Hill (1923) for human blood but somewhat different from that found by Redfield and Florkin (1931) for Urechis blood.The buffer value of plasma proteins is about twice as great, per unit weight, as that of human plasma proteins. Since the concentration f protein in skates plasma is one-third to one-half as great as in human plasma, it follows that the buffer value of plasma of the two species is about the sam...

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.

The heart rate of the sympathectomized dog in rest and exercise.

MUSCULAR exercise is accompanied by acceleration of the heart rate. The factors which determine this acceleration, and the heart rate attained in various standard degrees of exercise, have been studied in numerous experiments. After completely denervating the heart of a dog, and excluding chemical stimulation from the adrenal medulla and from the liver, Campos, Cannon, Lundin and Walker [1929] found that the heart rate was only slightly accelerated (12 beats at most), and that the muscular performance on a treadmill was greatly diminished. Samaan [1935], who performed a similar experiment after cutting the cardio-accelerators, except that he suppressed vagal impulses by atropine, noted that the heart rate never rose more than 18-29 beats instead of 110-130. His animals then performed the standard exercise with difficulty and showed intense signs of exhaustion. On the other hand, when the accelerator nerves alone were excluded by removal of the upper thoracic sympathetic chains, the dogs performed the standard work with apparent ease. Indeed Samaan makes the statement that in such animals, deprived of the nerves which positively make the heart beat more rapidly, the maximum capacity for doing work is markedly augmented. In dogs deprived of the cardio-accelerator and splanchnic innervations determinations of the maximal endurance show a definite increase of the capacity comparable with that observed in animals without cardio-accelerator sympathetic innervation according to S ama a n. However, the maximal tachycardia which was observed towards the end of the standard work was 105-121, an increase

Daily cycles of hibernation in the kangaroo rat, Dipodomys merriami

Abstract Thirty-six kangaroo rats were captured in the Mojave Desert near Las Vegas. Eight rats, group A, were kept at room temperature, 25 ± 2 °C. Ten, Group B, were kept at 13–15 °C and fed ad libitum. Eighteen, group C, were kept at 13–15 °C and fed only 2 g of dry oats daily. Rate of O2 consumption, VO2, food intake, rectal temperature, Tre., body weight and composition were measured in all groups. Group B showed a significant increase in VO2, and food intake and no change in Tre body weight as compared to group A. After 2 days on the limited food intake group C began to lose weight, and Tre then began to fluctuate ranging between 14 and 36 °C; the animals exhibited hibernation when the Tre was low. Eight of the 18 rats of group C reached Tre values of 14 °C or below; only one of these survived. The lowest Tre in the other 10 was 15 °C; all survived. Chemical analysis of the homogenized rats showed a significant decrease in body fat in group C to average 1.0% contrasted with 7.8% in group B and 3.7% in group A. The VO2 ranged from 1.9 ml/g hr at a Tre of 36.5 to 0.2 ml/g hr at a Tre of 15 °C. In conclusion D. merriami utilizes hibernation as an effective adaptive mechanism to carry out their essential body functions when on a limited food intake. It seems that maintaining a level of more than 1.5% of body fat is essential for successful arousal from hibernation.

Responses of Merriam's Kangaroo Rat to Heat

Kangaroo rats (Dipodomys) which live in the desert of the southwestern United States represent an outstanding example of adaptation to desert environment (Schmidt-Nielsen 1964a, pp. 150-178). Schmidt-Nielsen and Schmidt-Nielsen (1950) concluded that a primary factor in adaptation of Dipodomys merriami to desert environment is that it avoids high temperatures by remaining in burrows during the day. This view is supported by Carpenter (1966), who found that Dipodomys is seldom subject to high ambient temperature. However, Dawson (1955) has suggested that the presence of D. merriami in shallow burrows may indicate greater heat resistance than is possessed by other species of Dipodomys. He found that D. merriami and the diurnal antelope ground squirrel, Citellus leucurus frequently are exposed to high temperatures. The objective of our study was to examine selected physiological responses of winterand summer-acclimatized rats to heat, with the hope of interpreting the conflicting findings mentioned above.

Energetic Cost of Running in the Antelope Ground Squirrel Ammospermophilus leucurus

The energetic cost of running in small mammals has been of interest to various laboratories in recent years (Pasquis, Lacaisse, and Dejours 1970; Taylor, Schmidt-Nielsen, and Raab 1970; Yousef et al. 1970; Wunder 1970). This is due to the fact that fast locomotion is essential for survival of animals in their natural habitats. Animals must have the ability to search for food and to escape their prey. Exposure to cold and heat is known to alter the resting energy expenditure of small and large mammals (Yousef, Hahn, and Johnson 1968; Yousef and Dill 1970, 1971). However, the combined action of temperature and exercise on thermogenesis seems to vary from species to species. It is generally accepted that heat produced by exercise substitutes for shivering in man but not in small laboratory animals (Jansky 1965) or small wild animals (Hart and Heroux 1955; Yousef et al. 1970). Jansky (1965) suggested that differences between species do not depend on body weight or on their phylogeny. With the exception of our recent report (Yousef et al. 1970), there are no data on the influence of temperature on working heat production of desert mammals. On the contrary, several reports have been published on laboratory mammals and nondesert wild animals (Hart 1952; Hart and Heroux 1955;

Body composition and aerobic capacity of youth of both sexes.

ABSTRACTA review of recent papers reveals that as compared with non-athletes, athletes of both sexes have n greater blood volume, a greater red cell volume and an even greater plasma volume. Implicit in these facts their total hemoglobin is greater but their hemoglobin concentration is lower.Two gro

Biochemical properties of the blood of three equines

Abstract 1. 1. The hematocrit, hemoglobin, serum protein and serum chloride were determined on blood obtained from eleven burros, ten horses and six Shetland ponies. 2. 2. A comparison was made of the certain characteristics of blood of three equines compared to those of man. 3. 3. The measurements made revealed no significant differences between males and females. 4. 4. Men had higher hemoglobin values than equines. Variation in hemoglobin concentration in the blood of three equines was not significant. 5. 5. The concentration of hemoglobin in red cells is the same in equines and man. 6. 6. Serum protein is similar in equines and man. 7. 7. Serum chloride was significantly higher in the burrow than in the horse, pony and man. 8. 8. Variations from day to day in hematocrit and hemoglobin were negligible. 9. 9. Hemoglobin concentrations observed in two burros every two hr for 24 hr revealed a peak in the late afternoon.