Thermoregulatory Efficiency Research Articles

Effect of active warming-up on thermoregulatory, circulatory, and metabolic responses to incremental exercise in endurance-trained athletes.

The influence of 10 min warming-up at 40% VO2 max on thermal, circulatory, and metabolic responses to an incremental exercise to exhaustion as well as on the anaerobic threshold at the blood lactate level of 4 mmol.l-1 (AT) and the individual anaerobic threshold (IAT) was investigated in eight cross-country skiers. During exercise preceded by warming-up, the mean skin temperature (T sk) and external auditory canal temperature (Tac) did not change significantly in contrast to exercise without warming-up, producing a rise in both T sk and Tac (by approx. 1.2 degrees C and 1.1 degrees C, respectively). Warming-up did not alter the course of the rectal temperature changes during exercise. With warming-up skin humidity rose immediately after the beginning of exercise, whereas the onset of sweating without warming-up appeared much later at higher work intensities. Warming-up did not change the circulatory and ventilatory responses to incremental exercise and the oxygen uptake (VO2) either at submaximal or maximal work loads. With warming-up a significant increase was found in the threshold work load both at the AT and the IAT. The data demonstrated that warming-up has an advantageous effect on the efficiency of thermoregulation in endurance-trained athletes producing an early sweating response to the incremental exercise that results in attenuation of hyperthermia. An increase in the anaerobic threshold during incremental exercise preceded by warming-up may indicate an enhancement of the endurance capacity subsequent to warming-up.

Enhanced glucose availability for working muscles reduces exercise hyperthermia in dogs

Body temperature and metabolic responses to 2 h treadmill exercise in dogs given glucose intravenously (25-30 mg.kg-1 X min-1 throughout the run) were compared with those measured in the same animals with elevated plasma FFA concentrations (soya bean oil ingestion + intravenous heparin) and in control experiments (24 h fasting). In comparison with control conditions enhanced glucose availability for the working muscles caused a reduction in the exercise-induced increases in both rectal (by 0.9 +/- 0.11 degree C) and muscle (by 0.9 +/- 0.16 degree C) temperatures, a lower rate of oxygen uptake (by 16%) and an elevated respiratory exchange ratio. A tendency towards enhanced body temperature responses to exercise, accompanied by increases in VO2 and cardiac frequency was noted in dogs with elevated plasma FFA concentrations as compared with the control animals. The estimated amount of heat effectively dissipated from the body, expressed as a fraction of heat load (thermoregulatory efficiency) was significantly higher in dogs infused with glucose (0.962 +/- 0.0035), than in the controls (0.947 +/- 0.0043) and those with elevated plasma FFA concentrations (0.931 +/- 0.0029). It is concluded that the increased contribution of carbohydrates to the energy yield during exercise results in a marked attenuation of hyperthermia, associated with a reduced metabolic rate and improved thermoregulatory efficiency.

Influence of aging in the thermoregulatory efficiency of man.

Studies were carried out to evaluate the effect of aging on the thermoregulatory efficiency in man. The efficiency of thermoregulatory system was assessed on the basis of tolerance to acute cold stress, Tromp test and cold induced vasodilatation (CIVD) response. The experiments were done in 9 groups (15 each) of human volunteers in the age ranges of 20–25, 26–30, 31–35, 36–40, 41–45, 46–50, 51–55, 56–60 and 61–70 years. They were made to relax in a thermoneutral laboratory (27 ± 1‡C) for one hour; thereafter their resting heart rate, blood pressure, oxygen consumption, oral, mean skin, mean body and peripheral temperatures were measured. Then they were exposed to cold (10‡C) in a cold chamber wearing shorts and vests for two hours. The above parameters and shivering responses were recorded at 30 min intervals during cold exposures. On other occasions, their thermoregulatory efficiency test (Tromp Test) and cold induced vasodilatation response were also studied in the same thermoneutral laboratory. The results showed comparatively poor cold tolerance and thermoregulatory efficiency in elderly people. The middle aged category (above 40 years) showed a gradual reduction in the thermoregulatory efficiency, but highly significant reduction was noticed in those who exceeded sixty years of age.

Sezonowe zmiany termoregulacji i metabolizmu maksymalnego u myszy wielkookiej leśnej

Seasonal changes in thermoregulation efficiency and basal metabolism rate (BMR) were studied in Apodemus flavicollis (Melchior, 1834). The animals had significantly greater body weight in winter than in summer and the body weight of females differed significantly from that of males. The average rectal temperature in winter was 37.0±1.6°C.

Effects of doxapram on body temperature of the rat during radiofrequency irradiation.

Central nervous system stimulants can cause changes in body temperature and changes in susceptibility to high levels of radiofrequency radiation (RFR). In the present study, the effects of the central nervous system stimulant, doxapram, on thermal responses to 2.8 GHz pulsed RFR were examined in anaesthetized rats. During intermittent exposure to an average power density of 60 mW/cm2, doxapram significantly increased the time required for temperature to return to the pre-exposure level when irradiation was discontinued. When exposure was continued until lethal temperatures resulted, doxapram administration caused no significant change in survival time when compared to saline controls. Thus, although the drug decreased thermoregulatory efficiency during intermittent exposure to RFR, no change in susceptibility to terminal RFR exposure was observed.

Effect of ambient temperature on rectal temperature in normal and malnourished rats during early postnatal development.

Information on body temperature is frequently lacking in metabolic studies on normal and malnourished suckling rats although differences in their thermoregulatory efficiency may be expected. The aim of the present study was to evaluate the effect of different ambient temperatures on the rectal temperature of litters of normal and protein deprived rats to establish the ambient temperatures at which a normal rectal temperature can be expected at various postnatal ages. The offspring of normal rats and rats subjected to a dietary reduction of 50% of the protein intake were examined 10 days to 30 days postnatally. The pups were transferred from the nest cage to an incubator: the rectal temperature was measured immediately after transfer to the incubator and 30 and 60 min later at ambient temperatures of 35, 30 and 25 degrees C. Up to 15 days of age control pups showed a fall in rectal temperature after the short exposure to room temperature (22 degrees C) needed for transfer. A similar fall of rectal temperature was recorded in the malnourished pups up to 25 days age. The effects of the ambient temperatures on the malnourished pups indicated a delay in the control of body temperature of some 10 days. This is in agreement with a previous report on semi-starved rats (Heim & Szelenyi 1965). The conditions for the maintenance of a normal rectal temperature in litters of normal and malnourished suckling rats separated from their mother are out-lined.

Evidence for specific, cranial vasodilator control of lingual arteriovenous anastomoses in thermoregulation

1. 1. Spinal cord heating (s.c.h.) served to induce an increase in lingual blood flow and thermal polypnea in the anaesthetized dog. 2. 2. The thermoregulatory-induced increase in lingual blood flow could be reduced by the transection of either the chorda-lingual nerves (C.L.N.) or the lingual rami of the glossopharyngeal nerve (N.IX), and completely abolished by the transection of both nerves. 3. 3. The full thermoregulatory efficiency of thermla stimulation after transection of C.L.N. and N.IX was indicated by the unaffected polypneic response. 4. 4. It is suggested, that the thermoregulatory-induced vasodilatation in the canine tongue is due to the excitement of non-adrenergic vasodilator fibres, which are running in the C.L.N. as well as in the N.IX. 5. 5. It is assumed that the C.L.N. and the N.IX are mediating neural remote control of arteriovenous anastomoses in the canine tongue.

Neurophysiological Problems in Snow Bound High Altitude Areas

A series of studies have been conducted to evaluate the neurophysiological responses in young healthy soldiers during acclimatization at 3,500m altitude in Western Himalayas. The responses of autonomic nervous system, electroencephalogram hypothalamic thermoregulatory efficiency, orthostatic tolerance, sleep profile and effects of sleep deprivation have been studied in fresh inductees during three to five weeks of acclimatization at high altitude and compared with those of one year acclimatized lowlanders and high altitude natives. Physiological significance of these neurophysiological responses in the process of altitude adaptation is discussed in the light of current knowledge in the field.

Natural selection on body size and proportions in house sparrows

Variation in morphology across a species range is largely a function of climatic conditions. Evidence for this comes primarily from correlations of latitudinal trends of climate with those of body size or shape (the classic ecogeographic rules of Bergmann and Allen1). Few studies have documented a temporal sequence of natural selection on size variables within a single population2–7, and no study precisely documents selection on shape variables. For birds in temperate regions, winter climate can be a major source of mortality8, and is likely to be an important agent of selection on overall size2–6. We reported previously6 that severe winter weather produced significant changes in the distribution of size classes of a population of house sparrows (Passer domesticus). In that study, post-winter males were on average significantly larger than pre-winter males and post-winter females averaged significantly smaller than pre-winter females. We report here further analyses indicating that sparrows also undergo selection for refinement of bodily proportions, consistent with predictions from Allen's ecogeographic rule. Such selection for increased core-to-limb proportions probably results in greater thermoregulatory efficiency. The changes in proportions accompany the changes in overall size6 and there are major inter-sexual differences in how such proportions are achieved.

The Pattern of Behaviour of Rabbit Pups in the Nest

AbstractDomestic rabbit pups (22 litters of 6 pups each) were raised in plexiglass nest boxes, and their behaviour was studied under various experimental conditions during the first 14 days of life. 1. Rabbit pups show a stereotyped pattern of behaviour closely associated with the once daily nursing visit of the doe until they start to leave the nest on day 13. 2. One to two hours before nursing pups group tightly together and become exposed from the nest material. In young litters these behaviours appear to improve access to the doe's belly and to shorten the time the doe spends in the nest. 3. Rabbit pups are unusual in that they display a vigorous burst of post-nursing activity, i.e. simultaneous urination followed by digging and burrowing around the nest. This activity is triggered by the nursing act and appears to contribute to thermoregulatory efficiency as an insulating cover is quickly regained. 4. Within about 30 minutes pups reaggregate and remain well covered until the next nursing time. 5. The anticipatory uncovering appears to represent a circadian rhythm, and not to be simply due to hunger, as demonstrated in isolated litters deprived of one nursing. 6. Presumably the less time wild does spend in the nursery burrow the less chance there is of predators trapping them or finding the young. The ability of the pups to anticipate the nursing and the their thermoregulatory self-sufficiency may contribute to shortening the time rabbit does must spend in the nest.

Scrotal Lipomatosis

The anatomy of scrotal fat was studied histologically and by dissection in 28 normal cadavers and 44 idiopathic infertile subjects. Two fat patterns were described: normal and infertile. In the normal pattern, a small posterior extratunicary pad of fat was constantly encountered. Intratunicary fat occurred as small granules between the cord veins. Thirty-eight of the 44 idiopathic infertile subjects had scrotal lipomatosis, of which 2 types were recognised: extratunicary and intratunicary. The latter showed 2 patterns: diffuse and lobular. The diffuse pattern occurred in obese subjects and those of normal build, and the fat was firmly adherent to the cord veins. The lobular pattern occurred exclusively in the obese, and the lobules were loosely connected to the cord. The anatomical features of the normal fat pattern in relation to maximal testicular thermoregulatory efficiency were discussed. The role of scrotal lipomatosis in infertility was clarified and the relationship of scrotal lipomatosis to obesity presented.

The possible effect of meteorological stress on cancer and its importance for psychosomatic cancer research.

The various physiological mechanisms described, which are triggered by meteorological stimuli, may help to explain the effect of psychosomatic factors on cancer29. Whereas in purely psychosomatic research it may be difficult to study the real mechanisms involved, biometeorological studies on the effects of meteorological stress may assist future psychosomatic cancer research. Various studies suggest the great influence of thermoregulatory processes on the hormonal functions in the human body. Disturbance of these processes may lead to cancer development. Experiments byTromp andBouma have shown the very poor thermoregulatory efficiency of cancer patients. Studies byLea, Lee, McVay, Krasnow, Glaser, De Sauvage Nolting and others confirm the effect of meteorological stresses (in particular thermal stresses) on thermoregulatory processes and cancer development. The similarity in physiological processes during meteorological and psychological stresses may facilitate the studies on the influence of psychosomatic factors on cancer.

Net energetic and thermoregulatory efficiency during panting in the sheep

1. 1. The total heat production and that proportion attributable to panting, together with the total body and respiratory heat loss of shorn Merino sheep, were studied during exposure to various combinations of air temperature and humidity. 2. 2. While exposure to moderately hot environments resulted in panting with mean respiratory frequencies of up to 270 breaths min −1, the total heat production was not significantly higher than that in a thermoneutral environment and therefore the heat produced by panting appeared to be zero. 3. 3. The mean maximum heat loss through panting was approximately 60 per cent of the total heat loss and 56 per cent of the total heat production; this was due entirely to the evaporation of moisture. 4. 4. The results indicate that the sheep relies heavily on panting for heat dissipation and that in moderately hot environments the thermoregulatory efficiency of panting is high. 5. 5. It is concluded that, in the light of more recent observations, the method used here and in previous studies cannot be used to provide an estimate of the energy expenditure due to increased respiratory activity; rather, an estimate of the net change in metabolic rate is obtained.

Thermoregulatory efficiency of neonatal rabbit search for fur comfort contact.

Thermoregulatory efficiency of neonatal rabbit search for fur comfort contact.

Thermoregulatory efficiency of neonatal rabbit search for fur comfort contact.

Thermoregulatory efficiency of neonatal rabbit search for fur comfort contact.

Efficiency of thermoregulation in acutely cold-exposed young and old mice

Mice of different age (4–6 weeks and 1 year) were exposed to 0°. Whereas young animals showed a decrease of liver and muscle glycogen and an increase of non-esterified fatty acids in the serum, old mice did not mobilize their hepatic glycogen and increased their oxygen consumption to much less extent than young animals. Consequently, old mice, in contrast to young mice, were not able to maintain their normal body temperature.

Improvement of the thermoregulation efficiency of man above 1500 m altitude

Nachweis, dass vor allem atmosphärische Abkühlungsfaktoren Asthmaanfälle auslösen können und dass der menschliche Organismus über einer kritischen Höhe von 1500 m gegen solche Temperaturreize weniger empfindlich ist. Permanente Besserung nach wiederholter Höhenbehandlung.

Temperature regulation during continuous and intermittent exercise in man.

AbstractEkblom, B. C. J. Greenleaf, J. E. Greenleaf and L. Hermansen, Temperature regulation during continuous and intermittent exercise in man. Acta physiol. scand. 1971. 81. 1–10.Body temperature changes and heat dissipation responses were studied in three well‐trained men during moderately heavy (60 % of maximal aerobic power) continuous and intermittent exercise at the same average metabolic rate and heat production. The purpose was to determine if hypothetical “work factors” induced specifically by muscular activity influenced body temperature regulation. Compared with continuous work; a) the equilibrium level of rectal temperature (Tre) during intermittent work was elevated 0.35° C which accounted for 21 % of the total Tre increase from resting, and b) the decreased sweating of 32 g/(m2. hr) during intermittent work resulted in a decreased evaporative heat loss of 18.6 kcal/(m2. hr) that could account for the increased intermittent work Tre. These responses appear to be manifestations of reduced thermoregulatory efficiency due, perhaps, to non‐linearity in the relationship of body temperature to total work rate or to non‐linearity in the contribution of non‐thermal inputs at work rates above 100 % of max. V̇O2. It is also possible that other factors play a part, such as the frequency and duration of the work and rest cycles, rate of limb movement, or circulatory factors related to postural changes.

Temperature regulation of the unanesthetized cat during mild cold and severe heat stress.

ARTICLESTemperature regulation of the unanesthetized cat during mild cold and severe heat stressT. Adams, M. L. Morgan, W. S. Hunter, and K. R. HolmesT. Adams, M. L. Morgan, W. S. Hunter, and K. R. HolmesPublished Online:01 Dec 1970https://doi.org/10.1152/jappl.1970.29.6.852MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByA New Model for the Body Size–Metabolism RelationshipPhysiological and Biochemical Zoology, Vol. 83, No. 3Thermal effects on ventilation in cats: participation of carotid body chemoreceptorsRespiration Physiology, Vol. 86, No. 1Patterns of peripheral vasomotor function in near-natural conditions in the calf (Bos taurus)Comparative Biochemistry and Physiology Part A: Physiology, Vol. 77, No. 1Temperature regulation in adult quail (Colinus virginianus) during acute thermal stressComparative Biochemistry and Physiology Part A: Physiology, Vol. 74, No. 2Vasopressin and the regulation of evaporative water loss and body temperature in the catBrain Research, Vol. 251, No. 1Alterations in body temperature elicited by intrahypothalamic administration of tetrodotoxin, ouabain and A23187 ionophore in the conscious catBrain Research Bulletin, Vol. 5, No. 1Net energetic and thermoregulatory efficiency during panting in the sheepComparative Biochemistry and Physiology Part A: Physiology, Vol. 49, No. 3 More from this issue > Volume 29Issue 6December 1970Pages 852-858 Copyright & PermissionsCopyright © 1970 the American Physiological Societyhttps://doi.org/10.1152/jappl.1970.29.6.852PubMed5485356History Published online 1 December 1970 Published in print 1 December 1970 Metrics

Evolutionary Implications of Wing and Size Variation in the Red-Winged Blackbird in Relation to Geographic and Climatic Factors: A Multiple Regression Analysis

Power, Dennis M. (Royal Ontario Museum and Unive sity of Toronto, Torwto 5, Ont. Can.) 1969. Evolutionary implications of wing and size variation in the red-winged blackbird in relation to geographic and climatic factors: a multiple regression analysis. Syst. Zool., 18:363-373.-In red-winged blackbirds from central North America, geographic variation in wing length is a good indicator of geographic variation in body size. Multipli regression analysis is used to consider the relationship between geographic variation and eight geographic and climatic factors. Variation in males appears inversely related to two factors, latitude and July wet-bulb temperature, while variation in females is inversely related to only wet-bulb temperature. The statistical associations may indicate natural selection in terms of thermoregulatory efficiency. [Geographic variation. Thermoregulation. Multiple regression. Agelaius.] Speculation on the adaptive signifiance of' geographic variation is complicated by the fact that much of the genetic component of variation in a particular character may be the result of natural selection by more than one climatic, habitat, or biotic factor. Given a set of quantitative environmental factors which may be thought to relate in some way to variation in a character, a partial solution to the problem is in considering the statistical relationship between variation in the character and the enviromental factors by way of multiple regression analysis. The method yields, first, the multiple correlation coefficient which estimates the amount of variation