External work in level and grade walking on a motor-driven treadmill

1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
Author(s):  
J. W. Snellen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Total Energy Expenditure ◽  
The Body ◽  
External Work ◽  
Thermal Exchange ◽  
Level Walking ◽  
The Subject ◽  
Set Up ◽  
Physical Laws

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960

Heat Production and Heat Loss in the Dog at 8–36°C Environmental Temperature

1958 ◽  
Vol 194 (1) ◽  
pp. 99-108 ◽  
Author(s):  
H. T. Hammel ◽  
C. H. Wyndham ◽  
J. D. Hardy
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Vascular System ◽  
Heat Content ◽  
Important Change ◽  
The Body ◽  
Critical Temperatures ◽  
Hot Environment ◽  
Environmental Temperatures ◽  
Made In

Metabolic and thermal responses of three dogs were made in a rapid responding calorimeter at temperatures ranging from 8°C to 36°C. These dogs were acclimatized to a kennel temperature of 27°C and had critical temperatures between 23°C and 25°C. The only physiological responses to low environmental temperatures were a moderate decrease in total heat content and an increase in heat production. The tissue conductance and the cooling constant of the fur did not effectively decrease below the levels obtaining throughout the neutral zone. In a hot environment heat loss from the respiratory tract was greatly increased. Although there was a great increase in the tissue conductance in the hot environment, conductance of heat through the tissue became decreasingly important as the air temperature approached body temperature so that panting became increasingly important for maintaining thermal balance. It is concluded that the vasomotor response of the peripheral vascular system is primarily a mechanism for dissipating excess heat produced during exercise; it is practically unimportant as a heat conserving mechanism. Effective changes in the total insulation of the fur can only be achieved by changing the surface area of the body, particularly those areas which are thinly furred, and not by any important change in the fur thickness through pilomotor activity.

scholarly journals First year reading

1917 ◽  
Author(s):  
◽  
Frank F. Thompson
Keyword(s):  
Oral Reading ◽  
Subject Matter ◽  
The Body ◽  
First Year ◽  
Functional Connection ◽  
Reading Experience ◽  
Standard Set ◽  
The Subject ◽  
Psychology Of Reading ◽  
Set Up

This thesis will concern itself with first year reading, and it will have the following aims: 1. To examine the subject matter of first year reading in order to see what values the literature presuppose the child capable of controlling and appreciating, to find a criterion for selecting subject matter for first year reading, and to criticize the values found in first year reading in view of the standard set up. 2. To consider the methods of mastering the symbols; to try to find the most natural method of approach and of strongest motivation; and to outline the steps by which the symbols may be mastered in their functional connection with the reading experience. 3. To study the nature of the child and how he assimilates the author's experience by means of reconstructing his own; to make a limited survey of recent experiments in the psychology of reading and to note some of its implications as to first year reading. 4. To consider the body and voice as the mechanism for the expression of the values of the writer to others and to indicate how these are trained for effective expression. 5. To consider the part the audience plays in teaching to read and to suggest some plans by which this much neglected element in effective oral reading may be secured.

Thermal effects of dorsal head immersion in cold water on nonshivering humans

2005 ◽  
Vol 99 (5) ◽  
pp. 1958-1964 ◽  
Author(s):  
Gordon G. Giesbrecht ◽  
Tamara L. Lockhart ◽  
Gerald K. Bristow ◽  
Allan M. Steinman
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Thermal Effects ◽  
Cold Water ◽  
The Body ◽  
Whole Body ◽  
Esophageal Temperature ◽  
Confounding Effect ◽  
Core Cooling ◽  
Stimulation Of

Personal floatation devices maintain either a semirecumbent flotation posture with the head and upper chest out of the water or a horizontal flotation posture with the dorsal head and whole body immersed. The contribution of dorsal head and upper chest immersion to core cooling in cold water was isolated when the confounding effect of shivering heat production was inhibited with meperidine (Demerol, 2.5 mg/kg). Six male volunteers were immersed four times for up to 60 min, or until esophageal temperature = 34°C. An insulated hoodless dry suit or two different personal floatation devices were used to create four conditions: 1) body insulated, head out; 2) body insulated, dorsal head immersed; 3) body exposed, head (and upper chest) out; and 4) body exposed, dorsal head (and upper chest) immersed. When the body was insulated, dorsal head immersion did not affect core cooling rate (1.1°C/h) compared with head-out conditions (0.7°C/h). When the body was exposed, however, the rate of core cooling increased by 40% from 3.6°C/h with the head out to 5.0°C/h with the dorsal head and upper chest immersed ( P < 0.01). Heat loss from the dorsal head and upper chest was approximately proportional to the extra surface area that was immersed (∼10%). The exaggerated core cooling during dorsal head immersion (40% increase) may result from the extra heat loss affecting a smaller thermal core due to intense thermal stimulation of the body and head and resultant peripheral vasoconstriction. Dorsal head and upper chest immersion in cold water increases the rate of core cooling and decreases potential survival time.

The effect of environmental conditions on food utilisation by sheep

1959 ◽  
Vol 1 (1) ◽  
pp. 1-12 ◽  
Author(s):  
D. G. Armstrong ◽  
K. L. Blaxter ◽  
N. McC. Graham ◽  
F. W. Wainman
Keyword(s):  
Critical Temperature ◽  
Heat Loss ◽  
Heat Production ◽  
Environmental Conditions ◽  
Environmental Temperature ◽  
Heat Losses ◽  
The Body ◽  
Food Utilisation ◽  
Metabolisable Energy ◽  
Environmental Temperatures

1. A series of calorimetric experiments was conducted with sheep which had fleeces ranging in thickness from 0·1 cm. to 12 cm. at environmental temperatures between 8 and 32° C. Heat production, heat loss by radiation, by convection and conduction, by vaporisation of water and due to warming food and water to body temperature were measured together with losses of energy in faeces, in urine and as methane.2. The effects of a rise in environmental temperature on digestion of the food and on the loss of energy in urine or as methane resulted in a slight rise in the metabolisable energy of the ration by 6 Cal./° C.3. Environmental temperature had a marked effect on heat production, particularly when the fleece was short. The critical temperature (i.e. the environmental temperature at which heat production was minimal) of the closely-clipped sheep varied from 24° C. at a high level of feeding to 38°C. at a sub-maintenance level of feeding. These critical temperatures are similar to that of naked, resting man but much higher than that of the pig when fed similarly.4. As the fleece grew the critical temperature fell. Thus, on a maintenance level of feeding, a sheep with a fleece of 0·1 cm. had a critical temperature of 32° C.; when the fleece had grown to 2·5 cm. the critical temperature was 13° C. while with a 12 cm. fleece the critical temperature was 0° C.5. Below the critical temperature heat losses increase more rapidly in sheep with light fleeces. Thus a heavy fleece not only depresses the critical temperature but also reduces the rate of increase of heat loss with falling temperature under sub-critical conditions.6. At environmental temperatures well below the critical, the heat losses of the sheep per unit surface were identical. Under such conditions, when the whole of the metabolisable energy of the food is used to keep the animal warm, the criterion of ration adequacy is a high content of meta-bolisable energy in small bulk.7. At environmental temperatures above 32° C. the heat production on a constant ration increased, the rise being greatest with the highest level of feeding. Consequently the net energy value of the food declined at these high environmental temperatures.8. The calorimetric experiments were supplemented by two comparative feeding trials in which the effects of normal outdoor environmental conditions on the body weight of groups of Cheviot and Blackface sheep were measured. Control groups were kept indoors in heated pens.9. During the mild winter of 1956-7 the out-wintered Blackface wethers i n full fleece did not loose any more weight than those fed the same rations indoors.10. During the more severe winter of 1957-8, Cheviot, in-lamb ewes kept on a maintenance diet gained 2·3 lb.; those kept outside on the same ration lost 3·3 lb. With Blackface, in·lamb ewes the difference between the two groups was 0·3 lb. in favour of the indoor group.11. The food utilisation of sheep is affected considerably by environmental conditions. With little fleece the critical temperature is high and even when in full fleece an effect of cold can be demonstrated under practical conditions.

The physiology of heat regulation

1995 ◽  
Vol 268 (4) ◽  
pp. R838-R850 ◽  
Author(s):  
P. Webb
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Heat Content ◽  
The Body ◽  
Temperature Heat ◽  
Calorimetric Studies ◽  
Physiological Method ◽  
Related Level ◽  
Deep Body ◽  
Body Heat

Heat regulation is presented as the physiological method of handling metabolic heat, instead of temperature regulation. Experimental evidence of heat regulation from the literature is reviewed, including more than 20 years of calorimetric studies by the author. Changes in heat production are followed by slow exponential changes in heat loss, which produce changes in body heat storage. Heat balance occurs at many levels of heat production throughout the day and night, and at each level there is a related level of rectal temperature. Heat flow can be sensed by the transcutaneous temperature gradient. The controller for heat loss appears to operate like a servomechanism, with feedback from heat loss and possibly feedforward from heat production. Physiological responses defend the body heat content, but heat content varies over a range that is related to heat load. Changes in body heat content drive deep body temperatures.

Dynamic knee extension as model for study of isolated exercising muscle in humans

1985 ◽  
Vol 59 (5) ◽  
pp. 1647-1653 ◽  
Author(s):  
P. Andersen ◽  
R. P. Adams ◽  
G. Sjogaard ◽  
A. Thorboe ◽  
B. Saltin
Keyword(s):  
Femoral Vein ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Knee Extension ◽  
Bicycle Ergometer ◽  
The Body ◽  
External Work ◽  
Leg Muscles ◽  
Below The Knee ◽  
The Subject

In an attempt to approach a system of isolated exercising muscle in humans, a model has been developed that enables the study of muscle activity and metabolism over the quadriceps femoris (QF) muscles while the rest of the body remains relaxed. The simplest version includes the subject sitting on a table with a rod connecting the ankle and the pedal arm of a bicycle ergometer placed behind the subject. Exercise is performed by knee extension from a knee angle of 90 to approximately 170 degrees while flywheel momentum repositions the relaxed leg during flexion. Experiments where electromyographic recordings have been taken from biceps femoris, gastrocnemius, tibialis anterior, and other muscles in addition to QF indicate that only the QF is active and that there is an equal activation of the lateral, medial, and rectus femoris heads relative to maximum. Furthermore, virtually identical pulmonary O2 uptake (Vo2) during and without application of a pressure cuff below the knee emphasizes the inactivity of the lower leg muscles. The advantages of the model are that all external work can be localized to a single muscle group suitable for taking biopsies and that the blood flow in and sampling from the femoral vein are representative of the active muscles. Thus all measurements can be closely related to changes in the working muscle. Using this model we find that a linear relationship exists between external work and pulmonary Vo2 over the submaximal range and the maximal Vo2 per kilogram of muscle may be as much as twice as high as previously estimated.

scholarly journals Studies in the heat-production associated with muscular work. (Preliminary communication: section A.—Methods; section B.—Results.)

1913 ◽  
Vol 87 (593) ◽  
pp. 96-112
Keyword(s):  
Thermal Insulation ◽  
Heat Production ◽  
The Body ◽  
The Other ◽  
Air Space ◽  
Preliminary Communication ◽  
Sheet Copper ◽  
The Subject ◽  
Respiratory Gases ◽  
Radiator System

The calorimeter with which the included data have been obtained was built upon the plan described by Benedict, omitting, however, such parts as were essential rather to a study of the respiratory gases than to measurements of heat-production. The general principles of its construction are well known, exceedingly ingenious, were developed by Atwater and Benedict, and are briefly as follows: The body of the calorimeter is of sheet copper built upon an external wooden framework, on which again is built externally an outer zinc box enclosing, but nowhere in contact with, the calorimeter box proper. Between the two metal boxes, sets of thermocouples arranged in groups are utilised to discover any differences of temperature likely to lead to a radiation of heat from one box to the other across the intervening air space partially occupied by the wooden framework. In the walls of a still more external wooden shell are placed means by which heat may be added to or subtracted from the zinc box in a graduated fashion so as to annul any such observed differences in temperature. Thus the zinc box is kept in each of its several zones, each zone corresponding to a group of thermocouples, at the same temperature as the copper box, and the thermal insulation of the calorimeter is thus insured. The subject of the experiment enters the calorimeter by a window space left in the walls of this nest of boxes, and is then sealed in by glass and wax. The heat produced in his body, as well as the heat into which all his mechanical work is finally converted, raises the temperature (1) of an insulated radiator system through which a steady stream of water is maintained; (2) of the calorimeter box; (3) causes some evaporation of water from his respiratory passages and skin, and (4) tends to raise his own temperature. Each one of these four stores of heat is observed in suitable ways, and the summed account of their alterations provides a measure of the heat-production of, or total transformation of energy in, the subject.

XXI.—Observations on the Body Temperature of the Domestic Fowl (Gallus gallus) during Incubation

1911 ◽  
Vol 47 (3) ◽  
pp. 605-617 ◽  
Author(s):  
Sutherland Simpson
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Heat Production ◽  
Environmental Conditions ◽  
Seasonal Variations ◽  
Domestic Fowl ◽  
Gallus Gallus ◽  
The Body ◽  
Muscular Exercise

It is held by many that the body temperature shows certain fixed diurnal and seasonal variations which cannot be accounted for by the action of the various influences, such as muscular exercise, ingestion of food, sleep, etc., which are known to affect the rate of heat production and heat loss. These variations are believed to be associated with corresponding changes in the tissue activities, and to a large extent to be independent of environmental conditions.

Heat Balance and Distribution during the Core-Temperature Plateau in Anesthetized Humans

1995 ◽  
Vol 83 (3) ◽  
pp. 491-499. ◽  
Author(s):  
Andrea Kurz ◽  
Daniel I. Sessler ◽  
Richard Christensen ◽  
Martha Dechert
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Heat Production ◽  
Heat Balance ◽  
Thermal Flux ◽  
The Body ◽  
Metabolic Heat Production ◽  
The Core ◽  
Metabolic Heat ◽  
Temperature Plateau

Background Once triggered, intraoperative thermoregulatory vasoconstriction is remarkably effective in preventing further hypothermia. Protection results from both vasoconstriction-induced decrease in cutaneous heat loss and altered distribution of body heat. However, the independent contributions of each mechanism have not been quantified. Accordingly, we evaluated overall heat balance and distribution of heat within the body during the core-temperature plateau. Methods Nine minimally clothed male volunteers were anesthetized with propofol and isoflurane and maintained in an approximately 22 degrees C environment. They were monitored for approximately 2 h before vasoconstriction and for 3 h subsequently. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular temperatures, ten skin temperatures, and "deep" foot temperature. Heat constrained by vasoconstriction to the trunk and head was calculated by subtracting the expected change in that region (overall heat balance multiplied by the fractional weight of the trunk and head) from the actual change (change in distal esophageal temperature multiplied by the specific heat of human tissue and the weight of the trunk and head); the result represents the amount by which core heat exceeded that which would be expected based on overall heat balance, assuming that the change was evenly distributed throughout the body. Results Vasoconstriction and passive tissue cooling decreased heat loss but not to the level of heat production. Consequently, heat loss exceeded metabolic heat production throughout the study. Core temperature decreased approximately 1.3 C during the 2-h prevasoconstriction period; however, core temperature remained virtually constant during the subsequent 3 h. In the 3 h after vasoconstriction, arm and leg heat content decreased 57 +/- 9 kcal, and vasoconstriction constrained 22 +/- 8 kcal to the trunk and head. Conclusions These results confirm the efficacy of thermo-regulatory vasoconstriction in preventing additional core hypothermia. Decreased cutaneous heat loss and constraint of metabolic heat to the core thermal compartment contributed to the plateau.

A theoretical consideration of the means whereby the mammalian core temperature is defended at a null zone

2006 ◽  
Vol 100 (4) ◽  
pp. 1332-1337 ◽  
Author(s):  
John Bligh
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Heat Production ◽  
Reference Signal ◽  
Null Point ◽  
The Body ◽  
Physiological Basis ◽  
Temperature Changes ◽  
Effector Pathways ◽  
Response To Temperature

The neural process by which it is generally supposed that the stability of the body temperature of mammals is achieved has long been sought, but it remains unresolved. One hypothesis is that, as with many engineered physical systems, there is a stable reference signal with which a signal representative of body temperature is compared. Another hypothesis is that the differing coefficients of two signals that vary with temperature changes provide the set-level determinant. These could be the activities of the “cold” and “warm” sensors in response to temperature changes. Reciprocal crossing inhibition between the cold sensor to heat production effector pathways and the warm sensor to heat loss effector pathways through the central nervous system is a likely occurrence, and it could create the null-point temperature at which neither heat production nor heat loss effectors are active. This null point would be, seemingly, the set point at which body temperature is regulated. Neither hypothesis has been validated unequivocally. Students should be aware of this uncertainty about the physiological basis of homeothermy and, indeed, of homeostasis more generally. Perhaps we should be looking for a general principle that underlies the many physical and chemical stabilities of the internal environment, rather than considering them as quite separate accomplishments.

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