Cold-induced vasodilatation of finger and maximal oxygen consumption of young female athletes born in Hokkaido

To determine whether there is a direct correlation between endurance capacity and cold tolerance, maximal oxygen consumption (VO₂max), and cold-induced vasodilatation (CIVD), we measured these factors in 14 young female athletes born in Hokkaido, Japan's northernmost island. We determined the VO₂max by a standard incremental test on a cycle ergometer and measured the oxygen consumption (VO₂) by means of the Douglas-bag method. We determined the CIVD reaction by measuring the skin temperature of the left middle finger during immersion in cold water at 0°C for 20 min. The athletes showed significant positive correlations between VO₂max, expressed as l/min, and CIVD as well as other peripheral cold tolerance indexes (resistance index against frostbite and CIVD index). The body weight VO₂max (VO₂max/kg body weight) failed to correlate significantly with either the CIVD or with other cold tolerance indexes. These results suggest that CIVD in females may depend on factors other than those determined in this study, in addition to the functional spread of the vascular beds in peripheral tissues, including striated muscle; it is known that the size and the vascular bed in this tissue are affected by exercise training and that this results in the elevation of VO₂max and VO₂max/kg body weight.     

Physiological characteristics of cold acclimatization in man

Studies were conducted on 15 healthy young soldiers to evaluate the effect of a cold acclimatization schedule on the thermoregulatory and metabolic activity on exposure to acute cold stress. These men were exposed to cold (10C) for 4 h daily wearing only shorts for 21 days, in a cold chamber. They were subjected to a standard cold test at 10 ± 1C the day 1, 6, 11 and 21. The subjects were made to relax in a thermoneutral room (26–28C) for 1 h and their heart rate, blood pressure, oxygen consumption, oral temperature, mean skin temperature, mean body temperature, peripheral temperatures, and shivering activity were recorded. Then they were exposed to 10C and measurements were repeated at 30 min intervals, for 2 h. The cold induced vasodilatation (CIVD), cold pressor response and thermoregulatory efficiency tests were measured initially and at the end of acclimatization schedule. The data show that the procedure resulted in elevated resting metabolism, less fall in body temperature during acute cold stress, reduction in shivering, improvement in CIVD and thermoregulatory efficiency and less rise in BP and HR during cold pressor response. The data suggest the possibility of cold acclimatization in man by repeated exposure to moderately severe cold stress.     

Characterization of a three-phase response in gloved cold-stressed fingers

Seven gloves were studied worn by eight sedentary subjects (six men and two women) exposed to cold–dry, C–D, (mean dry bulb temperature −17.2^∘C; mean dew point temperature ), and cold–wet, C–W, ( 0^∘C; ) conditions. Mean endurance times were 75 min for the C–D and 162 min for the C–W conditions. A three-phase response pattern of the temperature in the fingers was characterized. Phase I comprised an initial period during which finger temperature remained close to the pre-exposed level, due to delayed vasoconstriction in the finger. Phase II involved an exponential-like decrease of finger temperature indicative of the onset of vasoconstriction in the finger. Phase III manifested periodic finger temperature changes due to cold induced vasodilatation (CIVD). Mean wave patterns for phase III indicated approximately 3.5 waves · h⁻¹ in the C–D but only about 2 waves · h⁻¹ in the C–W condition. Extension of endurance time, due to CIVD, was defined as the difference in time between the actual end of the experiment and the time the finger-tip would have reached the set temperature endurance limit as extrapolated by a continued exponential drop. Three overall response patterns of fingers in the cold were characterized: type A exhibiting all 3 phases; type B₁ or B₂ exhibiting either phases I+II or phases II+III; and type C showing only phase II. Considerable inter- and intra-subject variability was found. In both test conditions the final physiological thermal states of the subjects were between comfortable and slightly uncomfortable but acceptable and thus did not correlate with the responses in the fingers. Accepted: 5 January 1998     

Seasonal variation in basal and plastic cold tolerance: Adaptation is influenced by both long‐ and short‐term phenotypic plasticity

Understanding how thermal selection affects phenotypic distributions across different time scales will allow us to predict the effect of climate change on the fitness of ectotherms. We tested how seasonal temperature variation affects basal levels of cold tolerance and two types of phenotypic plasticity in Drosophila melanogaster. Developmental acclimation occurs as developmental stages of an organism are exposed to seasonal changes in temperature and its effect is irreversible, while reversible short‐term acclimation occurs daily in response to diurnal changes in temperature. We collected wild flies from a temperate population across seasons and measured two cold tolerance metrics (chill‐coma recovery and cold stress survival) and their responses to developmental and short‐term acclimation. Chill‐coma recovery responded to seasonal shifts in temperature, and phenotypic plasticity following both short‐term and developmental acclimation improved cold tolerance. This improvement indicated that both types of plasticity are adaptive, and that plasticity can compensate for genetic variation in basal cold tolerance during warmer parts of the season when flies tend to be less cold tolerant. We also observed a significantly stronger trade‐off between basal cold tolerance and short‐term acclimation during warmer months. For the longer‐term developmental acclimation, a trade‐off persisted regardless of season. A relationship between the two types of plasticity may provide additional insight into why some measures of thermal tolerance are more sensitive to seasonal variation than others.     

A new mathematical model to simulate AVA cold-induced vasodilation reaction to local cooling

The purpose of this work was to integrate a new mathematical model with a bioheat model, based on physiology and first principles, to predict thermoregulatory arterio-venous anastomoses (AVA) and cold-induced vasodilation (CIVD) reaction to local cooling. The transient energy balance equations of body segments constrained by thermoregulatory controls were solved numerically to predict segmental core and skin temperatures, and arterial blood flow for given metabolic rate and environmental conditions. Two similar AVA–CIVD mechanisms were incorporated. The first was activated during drop in local skin temperature (<32 °C). The second mechanism was activated at a minimum finger skin temperature, T _{CIVD, min}, where the AVA flow is dilated and constricted once the skin temperature reached a maximum value. The value of T _CIVD,min was determined empirically from values reported in literature for hand immersions in cold fluid. When compared with published data, the model predicted accurately the onset time of CIVD at 25 min and T _CIVD,min at 10 °C for hand exposure to still air at 0 °C. Good agreement was also obtained between predicted finger skin temperature and experimentally published values for repeated immersion in cold water at environmental conditions of 30, 25, and 20 °C. The CIVD thermal response was found related to core body temperature, finger skin temperature, and initial finger sensible heat loss rate upon exposure to cold fluid. The model captured central and local stimulations of the CIVD and accommodated observed variability reported in literature of onset time of CIVD reaction and T _CIVD,min.     

Analytical expressions for estimating endurance time and glove thermal resistance related to human finger in cold conditions

Frostbite is considered the severest form of cold injury and can lead to necrosis and loss of peripheral appendages. Therefore, prediction of endurance time of limb's tissue in cold condition is not only necessary but also crucial to estimate cold injury intensity and to choose appropriate clothing. According to the previous work which applied a 3-D thermal model for human finger to analyze cold stress, in this study, an expression is presented for endurance time in cold conditions to prevent cold injury. A formula is also recommended to select a proper glove with specific thermal resistance based on the ambient situation and cold exposure time. By employing linear extrapolation and real physical conditions, the proposed formulas were drawn out from numerical simulation. Analytical results show good agreement with numerical data. The used numerical data had been also validated with experimental data existed in the literature. Furthermore, the effect of different parameters such as glove thermal resistance and ambient temperature is investigated analytically.     

Effect of short-term cold temperature stress on development,survival and reproduction of Dysdercus koenigii (Hemiptera: Pyrrhocoridae)

Red cotton bug Dysdercus koenigii F. (Hemiptera: Pyrrhocoridae), is found destructive pest in various cotton growing areas. Under natural conditions insects are highly subjected to thermal stresses. In present work the developmental duration and survival rate of all immature stages, adult longevity and reproduction of D. koenigii by exposed to rapid changes in very low temperatures were studied. When 3 h short-stress of low temperatures (12–0 °C) was given to different stages of D. koenigii, the results revealed that survival rate of all stages were significantly reduced. Survival rate of female was significantly higher than male after exposed to cold temperature stress. Mating percentage, fecundity and hatching percentage were decreased significantly with the decrease of short-term cold temperature stress. Based on these results, we concluded that the developmental duration, survival rate and reproduction of D. koenigii significantly affected when they exposed to short term cold temperature stress.     

Validation of a model for prediction of skin temperatures in footwear

A model for foot skin temperature prediction was evaluated on the basis of 2 experiments on subjects at various environmental temperatures (light seated manual work at -10.7 degrees C (Study 1), and a short walking period in combination with standing and sitting at +2.8 degrees C, -11.8 degrees C and -24.6 degrees C (Study 2), with boots of 3 insulation levels. Insulation of the footwear was measured on a thermal foot model. Predicted and measured data showed a relatively good correlation (r = 0.87) at the 2 colder conditions in Study 2. The environmental temperature of 2.8 degrees C was not low enough at the chosen activity for a considerable foot skin temperature drop. In Study 1 the predicted temperature stayed higher for the whole exposure period and the difference between the predicted and the measured foot skin temperatures grew proportionally with time, while subsequent warm-up curves at room temperature were almost parallel. In Study 1 the correlation was 0.95. However, the paired t-test showed usually significant differences between measured and predicted foot skin temperatures. The insulation values from thermal foot measurements can be used in the model calculations. Lotens' foot model is lacking activity as direct input parameter, however, the blood flow is used instead (effect through Tcore). The Lotens foot model can give reasonable foot skin temperature values if the model limitations are considered. Due to the lack of activity level input, it will be difficult to make any good estimation of foot skin temperature during intermittent exercise. The rate of the foot temperature recovery after cold exposure was somewhat overestimated in the model--the warm-up of the feet of the subjects started later and was slower in the beginning of the warm-up than in the prediction. It could be useful to develop the model further by taking into consideration various wetness and activity levels.     

Reproducibility of the cold-induced vasodilation response in the human finger.

Cold-induced vasodilation (CIVD) is a cyclic oscillation in blood flow that occurs in the extremities on cold exposure and that is likely associated with reduced risk of cold injury (e.g., frostbite) as well as improved manual dexterity and less pain while working in the cold. The CIVD response varies between individuals, but the within-subject reproducibility has not been adequately described. The purpose of this study was to quantify the within-subject variability in the CIVD response under standardized conditions. Twenty-one volunteers resting in a controlled environment (27 degrees C) immersed the middle finger in warm water (42 degrees C) for 15 min to standardize initial finger temperature and then in cold water (4 degrees C; CWI) for 30 min, on five separate occasions. Skin temperature (Tf) and blood flow (laser-Doppler; expressed as percent change from warm-water peak) responses that describe CIVD were identified, including initial nadir reached during CWI, onset time of CIVD, initial apex during CIVD, time of that apex, and overall mean during CWI. Within-subject coefficient of variation for Tf across the five tests for the nail bed and pad, respectively, were as follows: nadir, 9 and 21%; onset, 18 and 19%; apex, 12 and 17%; apex time, 23 and 24%; mean 10 and 15%. For blood flow, these values were as follows: nadir 52 and 64%; onset, 6 and 5%; apex, 33 and 31%; apex time 9 and 8%; and mean 43 and 34%. Greater variability was found in the temperature response of the finger pad than the nail bed, but for blood flow the variability was similar between locations. Variability in onset and apex time between sites was similar for both temperature and blood flow responses. The reproducibility of the time course of CIVD suggests this methodology may be of value for further studies examining the mechanism of the response.     

Heat transfer analysis of skin during thermal therapy using thermal wave equation

Specifying exact geometry of vessel network and its effect on temperature distribution in living tissues is one of the most complicated problems of the bioheat field. In this paper, the effects of blood vessels on temperature distribution in a skin tissue subjected to various thermal therapy conditions are investigated. Present model consists of counter-current multilevel vessel network embedded in a three-dimensional triple-layered skin structure. Branching angles of vessels are calculated using the physiological principle of minimum work. Length and diameter ratios are specified using length doubling rule and Cube law, respectively. By solving continuity, momentum and energy equations for blood flow and Pennes and modified Pennes bioheat equations for the tissue, temperature distributions in the tissue are measured. Effects of considering modified Pennes bioheat equation are investigated, comprehensively. It is also observed that blood has an impressive role in temperature distribution of the tissue, especially at high temperatures. The effects of different parameters such as boundary conditions, relaxation time, thermal properties of skin, metabolism and pulse heat flux on temperature distribution are investigated. Tremendous effect of boundary condition type at the lower boundary is noted. It seems that neither insulation nor constant temperature at this boundary can completely describe the real physical phenomena. It is expected that real temperature at the lower levels is somewhat between two predicted values. The effect of temperature on the thermal properties of skin tissue is considered. It is shown that considering temperature dependent values for thermal conductivity is important in the temperature distribution estimation of skin tissue; however, the effect of temperature dependent values for specific heat capacity is negligible. It is seen that considering modified Pennes equation in processes with high heat flux during low times is significant.     

Genetic,acclimatizational and anthropometric factors in hand cooling among North and South Chinese

The left hands of unacclimatized North Chinese (N = 16) and South Chinese (N = 13) were exposed to 5°C water for 30 minutes followed by a 10 minute recovery period. Significant differences independent of body composition were found between the two samples on mean 30 minute temperature during immersion, time and temperature of the onset of initial CIVD (cold-induced vasodilation) at 0.01, 0.05 and 0.10 levels respectively. The result suggests the presence of a genetic component in the cold responses of Continental Asian populations and the possibility of the presence of a clinal distribution of cold response in Asia.     

Seasonal changes in thermal responses of urban residents to cold exposure

To determine whether urban circumpolar residents show seasonal acclimatisation to cold, thermoregulatory responses and thermal perception during cold exposure were examined in young men during January-March (n=7) and August-September (n=8). Subjects were exposed for 24 h to 22 and to 10 degrees C. Rectal (T(rect)) and skin temperatures were measured throughout the exposure. Oxygen consumption (VO(2)), finger skin blood flow (Q(f)), shivering and cold (CDT) and warm detection thresholds (WDT) were assessed four times during the exposure. Ratings of thermal sensations, comfort and tolerance were recorded using subjective judgement scales at 1-h intervals. During winter, subjects had a significantly higher mean skin temperature at both 22 and 10 degrees C compared with summer. However, skin temperatures decreased more at 10 degrees C in winter and remained higher only in the trunk. Finger skin temperature was higher at 22 degrees C, but lower at 10 degrees C in the winter suggesting an enhanced cold-induced vasoconstriction. Similarly, Q(f) decreased more in winter. The cold detection threshold of the hand was shifted to a lower level in the cold, and more substantially in the winter, which was related to lower skin temperatures in winter. Thermal sensations showed only slight seasonal variation. The observed seasonal differences in thermal responses suggest increased preservation of heat especially in the peripheral areas in winter. Blunted vasomotor and skin temperature responses, which are typical for habituation to cold, were not observed in winter. Instead, the responses in winter resemble aggravated reactions of non-cold acclimatised subjects.     

Cold-induced vasodilation and vasoconstriction in the finger of tropical and temperate indigenes

While heat acclimatization reflects the development of heat tolerance, it may weaken an ability to tolerate cold. The purpose of this study was to explore cold-induced vasodilation (CIVD) responses in the finger of tropical indigenes during finger cold immersion, along with temperate indigenes. Thirteen tropical male indigenes (subjects born and raised in the tropics) and 11 temperate male indigenes (subjects born and raised in Japan and China) participated. Subjects immersed their middle finger at 4.3±0.8 °C water for 30 min. Rectal temperature, skin temperatures, finger skin blood flow, blood pressure and subjective sensations were recorded during the test. The results showed that: (1) the tropical group demonstrated a lower minimum (T_min), maximum (T_max) and mean finger temperature (T_mean) compared to those of the temperate group (P<0.05); (2) seven tropical indigenes demonstrated a late-plateau type of CIVD pattern, which is characterized by a pronounced 1st vasoconstriction and a single CIVD with a faint and weak 2nd vasoconstriction, whereas no temperate indigene demonstrated the late-plateau type; and (3) the hand temperature at the end of finger immersion was 3 °C lower in the tropical than the temperate group (P<0.05). These results indicate that tropical indigenes have less active responses of arterio-venous anastomoses in the finger and weaker vasoconstrictions after the first CIVD response during finger cold immersion, which can be considered as being more vulnerable to cold injury of the periphery in severe cold.     

Thermal balance of cattle grazing winter range: Model development

Beef cattle grazing semi-arid foothill range of the Northern Rockies during winter may be exposed to cold temperatures and high winds while grazing pastures with low nutritional value. We refined a simple thermal balance equation to model heat exchange of free-ranging cattle. We account for the complex interactions between animal behavior and the changing natural environment by applying the components of the model to a rotating ellipsoid representing a cow at different orientations to the sun and wind. Correlation coefficients (r) between predicted standard operative temperature and measured surface temperature ranged from 0.82 on an individual basis to 0.88 on a herd average basis, indicating the model successfully quantifies heat exchanges of cattle exposed to cold conditions in the field.     

Cold-Induced Vasodilation during Single Digit Immersion in 0°C and 8°C Water in Men and Women

The present study compared the thermal responses of the finger to 0 and 8°C water immersion, two commonly used temperatures for cold-induced vasodilation (CIVD) research. On two separate and counterbalanced occasions 15 male and 15 female participants immersed their index finger in 20°C water for 5 min followed by either 0 or 8°C water for 30 min. Skin temperature, cardiovascular and perceptual data were recorded. Secondary analyses were performed between sexes and comparing 0.5, 1 and 4°C CIVD amplitude thresholds. With a 0.5°C threshold, CIVD waves were more prevalent in 8°C (2 (1 – 3) than in 0°C (1.5 (0 – 3)), but the amplitude was lower (4.0 ± 2.3 v 9.2 ± 4.0°C). Mean, minimum and maximum finger temperatures were lower in 0°C during the 30 min immersion, and CIVD onset and peak time occurred later in 0°C. Thermal sensation was lower and pain sensation was higher in 0°C. There were no differences between males and females in any of the physiological or CIVD data with the exception of SBP, which was higher in males. Females reported feeling higher thermal sensations in 8°C and lower pain sensations in 0°C and 8°C compared to males. Fewer CIVD responses were observed when using a 4°C (1 (0 – 3)) threshold to quantify a CIVD wave compared to using a 1°C (2 (0 – 3)) or 0.5°C (2 (0 – 3)) amplitude. In conclusion, both 0 and 8 °C can elicit CIVD but 8°C may be more suitable when looking to optimise the number of CIVD waves while minimising participant discomfort. The CIVD response to water immersion does not appear to be influenced by sex. Researchers should consider the amplitude threshold that was used to determine a CIVD wave when interpreting previous data.     

Effects of cold stress on juvenile Piaractus mesopotamicus and the mitigation by β-carotene

This study investigated the effects of cold stress on morphometrical and hematological biomarkers, energy metabolism, and oxidative stress in different tissues of P. mesopotamicus, and the protective role of β-carotene. Fish were fed with a control diet (CD) and the same diet supplemented with 105 mg/kg β-carotene (BD) for 60 days. After the feeding trial, fish fed CD or BD diets were exposed to control (24 °C) and low temperature (14 °C) for 24 h. Fish (CD and BD) exposed to thermal stress showed lower hepatosomatic index. The hemoglobin increased only in CD-fed fish exposed to 14 °C. Increased glycemia, plasmatic protein depletion, and decreased hepatic glycogen were observed in fish fed the CD, while only the lipid levels in liver were augmented in BD-fed fish exposed at 14 °C. Regarding the oxidative stress, increased antioxidant enzymes activity and lipid peroxidation were observed in CD-fed fish exposed to cold. The two-way ANOVA showed an interaction between dietary treatment and temperature for glucose and oxidative stress biomarkers, with the highest values recorded in 14 °C-exposed fish fed with the CD. Our study demonstrated that cold stress had the greatest impact on fish oxidative status, and β-carotene reduces harmful effects induced by cold in P. mesopotamicus.     

Effects on fetal and maternal body temperatures of exposure of pregnant ewes to heat, cold, and exercise.

We exposed Dorper-cross ewes at approximately 120-135 days of gestation to a hot (40 degrees C, 60% relative humidity) and a cold (4 degrees C, 90% relative humidity) environment and to treadmill exercise (2.1 km/h, 5 degrees gradient) and measured fetal lamb and ewe body temperatures using previously implanted abdominal radiotelemeters. When ewes were exposed to 2 h of heat or 30 min of exercise, body temperature rose less in the fetus than in the mother, such that the difference between fetal and maternal body temperature, on average 0.6 degrees C before the thermal stress, fell significantly by 0.54 +/- 0.06 degrees C (SE, n = 8) during heat exposure and by 0.21 +/- 0.08 degrees C (n = 7) during exercise. During 6 h of maternal exposure to cold, temperature fell significantly less in the fetus than in the ewe, and the difference between fetal and maternal body temperature rose to 1.16 +/- 0.26 degrees C (n = 9). Thermoregulatory strategies used by the pregnant ewe for thermoregulation during heat or cold exposure appear to protect the fetus from changes in its thermal environment.     

Changes in cold tolerance due to a 14-day stay in the Canadian Arctic

Responses to cold exposure tests both locally and of the whole body were examined in subjects who stayed in the Arctic (average maximum and minimum temperatures –11 and –21° C respectively) for 14 days of skiing and sleeping in tents. These changes were compared to responses in subjects living working in Ottawa, Canada (average max. and min. temperatures –5 and –11° C respectively). The tests were done before the stay in the Arctic (Pre), immediately after the return (Post 1) and approximately 32 days after the return (Post 2). For the whole-body cold exposure each subject, wearing only shorts and lying on a rope mesh cot, was exposed to an ambient temperature of 10° C. There was no consistent response in the changes of metabolic or body temperature to this exposure in either of groups and, in addition, the changes over time were variable. Cold induced vasodilatation (CIVD) was determined by measuring temperature changes in the middle finger of the nondominant hand upon immersion in ice water for 30 min. CIVD was depressed after the Arctic exposure whilst during the Post 2 testing, although variable, did not return to the Pre values; the responses of the control group were similar. These results indicate that normal seasonal changes may be as important in adaptation as a stay in the Arctic. Caution is advised in the separation of seasonal effects when examining the changes in adaptation after exposure to a cold environment.     

Can Winter-Active Bumblebees Survive the Cold? Assessing the Cold Tolerance of Bombus terrestris audax and the Effects of Pollen Feeding

There is now considerable evidence that climate change is disrupting the phenology of key pollinator species. The recently reported UK winter activity of the bumblebee Bombus terrestris brings a novel set of thermal challenges to bumblebee workers that would typically only be exposed to summer conditions. Here we assess the ability of workers to survive acute and chronic cold stress (via lower lethal temperatures and lower lethal times at 0°C), the capacity for rapid cold hardening (RCH) and the influence of diet (pollen versus nectar consumption) on supercooling points (SCP). Comparisons are made with chronic cold stress indices and SCPs in queen bumblebees. Results showed worker bees were able to survive acute temperatures likely to be experienced in a mild winter, with queens significantly more tolerant to chronic cold temperature stress. The first evidence of RCH in any Hymenoptera is shown. In addition, dietary manipulation indicated the consumption of pollen significantly increased SCP temperature. These results are discussed in the light of winter active bumblebees and climate change.     

Thermoregulation during cold exposure: effects of prior exercise.

This study examined whether acute exercise would impair the body's capability to maintain thermal balance during a subsequent cold exposure. Ten men rested for 2 h during a standardized cold-air test (4.6 degrees C) after two treatments: 1) 60 min of cycle exercise (Ex) at 55% peak O(2) uptake and 2) passive heating (Heat). Ex was performed during a 35 degrees C water immersion (WI), and Heat was conducted during a 38.2 degrees C WI. The duration of Heat was individually adjusted (mean = 53 min) so that rectal temperature was similar at the end of WI in both Ex (38.2 degrees C) and Heat (38.1 degrees C). During the cold-air test after Ex, relative to Heat 1) rectal temperature was lower (P < 0.05) from minutes 40-120, 2) mean weighted heat flow was higher (P < 0.05), 3) insulation was lower (P < 0.05), and 4) metabolic heat production was not different. These results suggest that prior physical exercise may predispose a person to greater heat loss and to experience a larger decline in core temperature when subsequently exposed to cold air. The combination of exercise intensity and duration studied in these experiments did not fatigue the shivering response to cold exposure.