Effects of wearing two different types of clothing on body temperatures during and after exercise

The experiment was conducted to investigate the human thermoregulatory responses during rest, exercise and recovery atT _a 20°C and 60% R.H. under the conditions of wearing two different types of clothing. Six healthy men wore two types of clothing: one covering the whole body area except the head (Type A, weight 1656 g), and the other covering only the trunk, upper arms and thighs (Type B, weight 996 g). The level of rectal temperature was kept significantly higher in Type B than in Type A during rest and recovery. The increased and decreased rates of rectal temperature during exercise and recovery were significantly greater in Type A than in Type B, respectively. These findings are discussed from the viewpoint of the differences of skin temperatures of the extremities between Type A and Type B.     

Different thermal conditions of the extremities affect thermoregulation in clothed man

The effects of different types of clothing on human deep body temperature were studied with six healthy male subjects in a supine posture. Two clothing ensembles were employed for the present study: A covered the whole body area with garments except the face (1.97 clo) and B covered only the trunk and the upper half of the extremities with garments (1.53 clo). The experiment was carried out in a climatic chamber at 55% ± 5% relative humidity under cooling and warming temperatures: the temperature was changed from 22°C to 10°C (cooling) and returned to 22°C again (warming). The major findings were: rectal temperature (T _re) continued to decrease gradually in A throughout the experiment, whereas in B it increased during cooling, and returned to previous levels during warming. As a result, Tre and chest skin temperature were maintained at a higher level in B than in A. Internal tissue conductances were greater in A than in B both during cooling and during warming. Thermal comfort appeared to have been influenced more by the rate of skin temperature change than by the level of skin temperature per se. It was concluded that peripheral vasoconstriction in B induced less heat flow from core to shell, and, thus, the core temperature was maintained at a higher level in B than in A.     

Physiological significance of hydrophilic and hydrophobic textile materials during intermittent exercise in humans under the influence of warm ambient temperature with and without wind

The purpose of this present study was to compare the physiological effects of the hydrophilic and hydrophobic properties of the fabrics investigated in exercising and resting subjects at an ambient temperature of 30°C and a relative humidity of 50% with and without wind. Three kinds of clothing ensemble were tested: wool and cotton blend with high moisture regain (A), 100% cotton with intermediate moisture regain (B), 100% polyester clothing with low moisture regain (C). The experiments were performed using seven young adult women as subjects. They comprised six repeated periods of 10-min exercise on a cycle ergometer at an intensity of 40% maximal oxygen uptake followed by 5 min of rest (20 min for the last rest). The experiments comprised two sessions. During session I (first three repetitions of exercise and rest) the subjects were exposed to an indifferent wind velocity and during session II (last three repetitions of exercise and rest) they were exposed to a wind velocity of 1.5 m · s⁻¹. Rectal temperature and skin temperatures at eight sites, pulse rate and clothing microclimate were recorded throughout the whole period. The main findings can be summarized as follows: rectal temperature during session II was kept at a significantly lower level in A than in B and C. Clothing microclimate humidity at the chest was significantly lower in A than in B and C during session II. Skin and clothing microclimate temperatures at the chest were significantly lower in A than in B and C during session II. Pulse rate was significantly higher in C than in A and B during sessions I and II. It was concluded that the hydrophilic properties of the fabrics studied were of physiological significance for reducing heat strain during exercise and rest especially when influenced by wind. Accepted: 3 June 1998     

The effects of fabric air permeability and moisture absorption on clothing microclimate and subjective sensation in sedentary women at cyclic changes of ambient temperatures from 27 degrees C to 33 degrees C

The present paper aimed at learning the effects of two different levels of air permeability and moisture absorption on clothing microclimate and subjective sensation in sedentary women. Three kinds of clothing ensemble were investigated: 1) polyester clothing with low moisture absorption and low air permeability (A clothing); 2) polyester clothing with low moisture absorption and high air permeability (B clothing); and 3) cotton clothing with high moisture absorption and high air permeability (C clothing). After 20 min of dressing time, the room temperature and humidity began to rise from 27 degrees C and 50% rh to 33 degrees C and 70% rh over 20 min, and it was maintained for 30 min (Section I); it then began to fall to 27 degrees C and 50% rh over 20 min, and it was maintained there for 20 min (Section II). The subject sat quietly on a chair for 110 min. The main findings are summarized as follows: 1) The clothing surface temperature was significantly higher in C clothing than in B clothing during section I, but it was significantly higher in B clothing than in C clothing during section II. 2) Although the positive relationship between the microclimate humidity and forearm sweat rate was significantly confirmed in all three kinds of clothing, the microclimate humidity at the chest for the same sweat rate was lower in C clothing than in A and B clothing. These results were discussed in terms of thermal physiology.     

Seasonal adaptation of thermal and metabolic responses in men wearing different clothing at 10° C

Thermoregulatory responses at ambient temperatures of 20 and 10° C in six male subjects wearing two different kinds of clothing were compared between summer and winter. The two different kinds of clothing were one insulating the upper half of the body lightly and the lower half of the body heavily (clothing A, the weight in the upper and lower halves of the body being, respectively, 489 g and 1278 g) and the other insulating the upper half of the body heavily and the lower half of the body lightly (clothing B: 1212 g and 559 g). The major findings are summarized as follow. (i) Rectal temperature was kept significantly higher in clothing B than in clothing A both in summer and winter. (ii) The fall of rectal temperature was significantly greater in summer than in winter in both types of clothing. (iii) Mean skin temperatures and skin temperatures in the face, chest, thigh and leg were significantly lower atT _a of 10° C in summer than in winter in clothing A, while skin temperatures in the face and thigh were also significantly lower atT _a of 10° C in summer than in winter in clothing B. (iv) Metabolic heat production was higher in summer than in winter at 20 and 10° C in both types of clothing. (v) The subjects felt cooler and colder toT _a of 10° C in summer than in winter in both types of clothing. These different responses occurring between summer and winter are discussed mainly in terms of total conductance and dry heat loss.     

Effects of Two Types of Clothing on the Day-Night Variation of Core Temperature and Salivary Immunoglobulin a

Circadian variations in core temperature, skin temperatures, heart rate, and salivary immunoglobulin A (IgA) were compared in subjects wearing two different types of clothing that covered, or left uncovered, their extremities. The experiments were carried out on six female subjects at an ambient temperature of 24 ± 0.5°C and relative humidity of 50 ± 5%. One type of clotiiing consisted of long-sleeved shirts, full-length trousers, and socks (Type L: 1042 g, 1.048 clo); the other was half-sleeved shirts and knee-length trousers (Type H: 747 g, 0.744 clo). The main results were as follows: (i) The level of rectal temperature during night sleep was significantly lower with Type H than Type L clothing, and cosinor analysis indicated a significantly higher circadian amplitude with Type H clothing, (ii) Skin temperatures in the lower extremities increased significantly more on retiring to sleep with Type H than Type L clothing, (iii) Heart rate was significantly lower with Type H than Type L clothing during the sleep period, (iv) The day-night variation of salivary IgA showed a pattern that was the inverse of that of rectal temperature (i.e., low in the daytime and high in the nighttime), and the concentration of salivary IgA was significantly higher with Type H than Type L clothing at 02:30. (v) Subjectively, the self-assessed sleep quality was better with Type H clothing. These results suggest that clothing that leaves the extremities uncovered might be regarded as favorable at the moderate temperature since it induces good sleep and activates the immune response. (Chronobiology International, 14(6), 607–617, 1997)     

Cooling different body surfaces during upper and lower body exercise

The effect of varying the body surface area being cooled by a liquid microclimate system was evaluated during exercise heat-stress conditions. Six male subjects performed a total of six exercise (O2 uptake = 1.2 l/min) tests in a hot environment (ambient temperature = 38 degrees C, relative humidity = 30%) while dressed in clothing having low moisture permeability and high insulation. Each subject completed two upper body exercise (U; arm crank) tests: 1) with only the torso surface (T) cooled; and 2) with the surfaces of both the torso and upper arms (TA) cooled [coolant temperature at the inlet (Ti) was 20 degrees C for all upper body tests]. Each subject also completed four lower body exercise (L; walking) tests: 1) with only the T cooled (Ti = 20 degrees C); 2) with only the T cooled (Ti = 26 degrees C); 3) with torso, upper arm, and thigh surface (TAT) cooled (Ti = 20 degrees C); and 4) with TAT cooled (Ti = 26 degrees C). During U exercise, TA cooling had no effects compared with cooling only T. During L exercise, sweat rates, heart rates, and rectal temperature (Tre) changes were less with TAT cooling compared with cooling only the T. Altering Ti had no effect on Tre changes, but higher heart rates were observed with 26 than with 20 degrees C. These data indicate that cooling arms during upper body exercise provides no thermoregulatory advantage, although cooling the thigh surfaces during lower body exercise does provide an advantage.     

Evaluation on masks with exhaust valves and with exhaust holes from physiological and subjective responses

The purpose of this study was to compare the effects of wearing different kinds of masks on the ear canal temperature, heart rate, clothing microclimate, and subjective perception of discomfort. Ten subjects performed intermittent exercise on a treadmill while wearing the protective masks in a climatic chamber controlled at an air temperature of 25 degrees C and a relative humidity of 70%. Two types of mask-mask A, with exhaust valves and mask B, with exhaust holes-were used in the study. The results of this study indicated: (1) The subjects had a tendency toward lower maximum heart rate when wearing mask A than when wearing mask B. (2) Temperatures and absolute humidities (the outer surface of mask, the microclimate inside the mask, the chest wall skin and microclimate) of mask A were significantly lower than those of mask B. (3) The ear canal temperature increased significantly in mask B as compared to that in mask A. (4) The ear canal temperature showed significant augmentation along with increased temperature and humidity inside the mask microclimate. The mask microclimate temperature also affected significantly the chest microclimate temperature. (5) Mask A was rated significantly lower for perception of humidity, heat, breath resistance, tightness, unfitness, odor, fatigue, and offered less overall discomfort than mask B. (6) Subjective preference for mask A was higher. (7) The ratings of subjective overall discomfort showed significant augmentation along with increased wetness and fatigue. We discuss how the ventilation properties of masks A and B induce significantly different temperature and humidity in the microclimates of the masks and the heat loss of the body, which have profound influences on heart rate, thermal stress, and subjective perception of discomfort.     

Effect of hygroscopic fabrics on wear comfort in the fluctuating microclimate of clothing

1. 1. A new type of simulator for clothing microclimate was designed and constructed.

2. 2. The simulator was designed to simulate the humidity fluctuation of clothing microclimate as observed under light working conditions and to measure the surface temperature of sample fabrics against the skin by means of a radiation thermometer.

3. 3. Knitted fabrics of cotton and polyester, and polyethylene films were used as specimens with different hygroscopicities.

4. 4. The quick rise and fall in the surface temperature of cotton fabric was observed under rapid fluctuations of the microclimate humidity.

5. 5. Under the same humidity fluctuations, the temperature of polyester fabric rose and fell more moderately than that of cotton fabrics, and the temperature of the polyethylene film did not change. When the rate of change in stimulus temperature is higher, the threshold temperature of warm sensation of the skin comes closer to a given adaption temperature.

6. 6. Therefore, the rapid and large changes in the fabric temperature against the skin, which were observed especially for hygroscopic cotton fabric, must affect the thermal comfort of clothing.

The effects of two types of clothing on seasonal cold tolerance

This study investigated the effects of two types of clothing, leaving legs covered or uncovered, on seasonal cold tolerance in women. Experiments were carried out to compare cold tolerance at an ambient temperature (T _a) of 10° C in December between two groups of subjects, who wore either knee-length skirts (skirt group) or full-length trousers (trouser group) for 3 months from September to November. The main results are summarized as follows: rectal temperatures continued to fall for 40 min in the trouser group when the subjects were covered by a blanket, while it became stable in 30 min in the skirt group; rectal temperatures showed greater increases in the skirt group when the blanket was removed after 40 min exposure to T _a of 10° C; metabolic heat production was kept significantly lower in the skirt group when uncovered or covered by a blanket at T _a of 10° C; metabolic heat production was negatively correlated with mean skin temperature and was always higher in the trouser group when measured at the same mean skin temperature; in the uncovered condition diastolic blood pressure increased significantly in the trouser group but not in the skirt group. These results would suggest that the subjects who wore skirts for 3 months from September to November had improved their ability to tolerate the cold.     

Influence of body heat content on hand function during prolonged cold exposures.

We examined the influence of 1) prior increase [preheating (PHT)], 2) increase throughout [heating (HT)], and 3) no increase [control (Con)] of body heat content (H(b)) on neuromuscular function and manual dexterity of the hands during a 130-min exposure to -20 degrees C (coldEx). Ten volunteers randomly underwent three passive coldEx, incorporating a 10-min moderate-exercise period at the 65th min while wearing a liquid conditioning garment (LCG) and military arctic clothing. In PHT, 50 degrees C water was circulated in the LCG before coldEx until core temperature was increased by 0.5 degrees C. In HT, participants regulated the inlet LCG water temperature throughout coldEx to subjective comfort, while the LCG was not operating in Con. Thermal comfort, rectal temperature, mean skin temperature, mean finger temperature (T(fing)), change in H(b) (DeltaH(b)), rate of body heat storage, Purdue pegboard test, finger tapping, handgrip, maximum voluntary contraction, and evoked twitch force of the first dorsal interosseus muscle were recorded. Results demonstrated that, unlike in HT and PHT, thermal comfort, rectal temperature, mean skin temperature, twitch force, maximum voluntary contraction, and finger tapping declined significantly in Con. In contrast, T(fing) and Purdue pegboard test remained constant only in HT. Generalized estimating equations demonstrated that DeltaH(b) and T(fing) were associated over time with hand function, whereas no significant association was detected for rate of body heat storage. It is concluded that increasing H(b) not only throughout but also before a coldEx is effective in maintaining hand function. In addition, we found that the best indicator of hand function is DeltaH(b) followed by T(fing).     

Efficacy of intermittent, regional microclimate cooling.

The vasomotor response to cold may compromise the capacity for microclimate cooling (MCC) to reduce thermoregulatory strain. This study examined the hypothesis that intermittent, regional MCC (IRC) would abate this response and improve heat loss when compared with constant MCC (CC) during exercise heat stress. In addition, the relative effectiveness of four different IRC regimens was compared. Five heat-acclimated men attempted six experimental trials of treadmill walking ( approximately 225 W/m(2)) in a warm climate (dry bulb temperature = 30 degrees C, dewpoint temperature = 11 degrees C) while wearing chemical protective clothing (insulation = 2.1; moisture permeability = 0.32) with a water-perfused (21 degrees C) cooling undergarment. The six trials conducted were CC (continuous perfusion) of 72% body surface area (BSA), two IRC regimens cooling 36% BSA by using 2:2 (IRC(1)) or 4:4 (IRC(2)) min on-off perfusion ratios, two IRC regimens cooling 18% BSA by using 1:3 (IRC(3)) or 2:6 (IRC(4)) min on-off perfusion ratios, and a no cooling (NC) control. Compared with NC, CC significantly reduced changes in rectal temperature ( approximately 1.2 degrees C) and heart rate ( approximately 60 beats/min) (P < 0.05). The four IRC regimens all provided a similar reduction in exercise heat strain and were 164-215% more efficient than CC because of greater heat flux over a smaller BSA. These findings indicate that the IRC approach to MCC is a more efficient means of cooling when compared with CC paradigms and can improve MCC capacity by reducing power requirements.     

Factors affecting the resistance to heat transfer provided by clothing

1. 1. This paper discusses the factors that affect the insulation and evaporative resistance provided by clothing.

2. 2. These include: fabric thickness and density, the amount of body surface area covered by garments, the evenness of the distribution of fabrics over the body surface, the increase in surface area for heat loss due to clothing, the looseness or tightness of fit, a person's body position (seated vs standing), body motion and wind.

Formation of 8-nitroguanine in tobacco cigarette smokers and in tobacco smoke-exposed Wistar rats

Our previous studies have shown that 8-nitroguanine (8-NO(2)-G) could serve as a specific biomarker of DNA damage induced by gaseous nitrogen oxides (NO(x)) exposure. To evaluate the effect of tobacco cigarette smoking on the DNA damage in peripheral lymphocytes of cigarette smoke ones, we randomly collected and determined the level of 8-NO(2)-G in DNA extracted from peripheral lymphocyte of 15 each of light-smoking healthy volunteer (L-S, less than one pack per day), moderate-smoking healthy volunteers (M-S, one to two pack per day for 5-10 years), heavy-smoking healthy volunteers (H-S, over two packs per day for 10 years), lung cancer patients with heavy smoking (cancer H-S) and non-smoking healthy controls. Both of the mean level of the 8-NO(2)-G levels in peripheral lymphocyte (0.90+/-1.0, 1.23+/-1.14, 1.43+/-0.79, 3.62+/-1.38 ng per microg DNA) and serum nitrite (38.99+/-9.58, 46.70+/-9.38, 55.46+/-10.45, 70.1+/-18.54 microM) of L-S, M-S, H-S and cancer H-S groups were higher than that of non-smoking healthy controls (0.02+/-0.04 and 18.96+/-4.31 for 8-NO(2)-G level and serum nitrite, respectively). Furthermore, in animal experiment, a dose-dependent increase in 8-NO(2)-G was observed in rat lung and peripheral lymphocyte DNA of Wistar rats after tobacco cigarette smoke exposure twice a day, for 1 month. The level of 8-NO(2)-G is 0.17+/-0.41, 1.65+/-3.15, 23.50+/-20.75 and 37.58+/-17.55 ng per microg lung DNA for rat exposed with tobacco cigarette smoke from 0, 5, 10, 15 cigarettes per day, respectively. It was also found that count of peripheral lymphocytes and nitrite concentration in serum of rat increased after the tobacco smoke exposure. It is postulated that tobacco cigarette smoking could induce DNA damage (8-NO(2)-G formation) by exo- and endogenous NO(x).     

Thermophysiological responses under the influences of two types of clothing at an ambient temperature of 32 degrees C with sun radiation

This study aimed to examine the different thermophysiological responses between two types of clothing (HALF, shirts with half sleeves and knee-length trousers; and LONG, shirts with long sleeves and long trousers) in a warm environment with artificial sun radiation. Seven females volunteered as subjects. The subject sat on a balance for 1 h in a climatic chamber with artificial sun. The artificial sun radiation was 600 kcal.m-2.h-1 in front of the subject. The ambient temperature was increased gradually from 27 to 31 degrees C over the experimental period. The globe temperature also increased from 27 to 43 degrees C in 15 min and was kept at 44 degrees C on additional 45 min. The main results were summarized as follows: 1) Extent of rise in rectal and mean skin temperatures during 1 h exposure was significantly higher in HALF than in LONG. 2) Local sweat rate was greater in HALF. 3) The subjects felt wetter and less comfortable in LONG. These results suggest that LONG could weaken heat stress when the subjects were exposed to sun radiation even under moderate warm ambient temperature.     

Effects of a five-hour exposure of arm and leg to a slightly cool thermal environment in the afternoon on the body temperature rhythm

The purpose of this study was to determine whether the different thermal conditions of the arm and leg due to wearing different types of clothing during the afternoon could modulate the circadian rhythm of body temperature and subjective sleep quality. Six healthy female volunteers were studied twice with two types of clothing, leaving the arm and leg covered or uncovered. The environmental chamber was controlled at 24 ± 0.5°C and 50 ± 5% RH during wakefulness and 28 ± 0.5°C and 50 ± 5% RH during night sleep. One type of clothing consisted of long-sleeved shirts and full-length trousers (Type L, 989 g, 0.991 clo); the other type was of half-sleeved shirts and knee-length trousers (Type H, 750 g, 0.747 clo). One testing session lasted for 16 h from 14:00 to 06:00 h the next morning. Subjects wore Type L or Type H clothing during the afternoon exposure (14:00 - 19:00), and Type L clothing during the evening (19:00 - 22:30 h) and the night sleep (22:30 - 06:00 h). Results were as follows. (1) When wearing Type H rather than Type L clothing, skin temperatures of the arm and leg were significantly lower during the time of exposure, and increased more after the evening. (2) Rectal temperature was not significantly different between the two types of clothing except during the early part of the exposure period, but it decreased during the evening by a significantly greater amount when wearing Type H clothing. (3) Subjective sleep quality was not significantly different between the two clothing types. These results suggest that afternoon exposure of the arm and leg to a slightly cool environment does not have a strong after-effect on the body temperature and subjective sleep quality.     

Circadian variation of rectal temperature in newborn sheep

In adult animals, body temperature shows a 24 h rhythm that is endogenously generated. We examined the existence of 24 h rhythms of temperature in 10 newborn sheep. Four newborns, aged 5 to 28 days were kept with their mothers under nycthemeral conditions, and the remaining 6 lambs, aged 21 to 43 days, were kept with their mothers in constant light from day 3 after birth. Experiments were performed with both groups of lambs in the laboratory. Additional experiments were performed with the 6 lambs kept under constant light while they were in the pen with their mothers to rule out artifacts due to manipulation or artificial feeding. During the experiments done in the laboratory, the lambs were kept blindfolded in a canvas sling and were fed baby formula approximately every four hours (lambs kept under nycthemeral conditions) or every hour (constant light lambs). Lights were on in the room during the whole experiment. Temperature in the room was maintained at 18 +/- 0.1 degrees C (mean +/- SEM). In the experiments done in the pen, animals remained with the mother and room temperature was not controlled. In all experiments, rectal temperature was hourly measured for 24 h with a thermocouple inserted in the lamb's rectum and connected to a Philipp Schenk digital recorder. Lambs kept under nycthemeral conditions show a variation of mean rectal temperature (t degree) with a period of 24 h, that fits a cosine function (P less than 0.001): Rectal t degree (degree C) = 40.6 + 0.4 cos [15 (t-16.22)]. The mesor is 40.6, the amplitude 0.4, and the acrophase expressed in h is 16.22 (n = 4). Lambs kept under constant light show a variation of rectal temperature with a period of 24 h, independently of whether the measurements were done in the laboratory or in the pens. The acrophases varied widely in these animals, when the acrophase were synchronized so theta = 2400, mean rectal temperature showed a variation with a period of 24 h that fits the equation (P less than 0.001): Rectal t degree (degree C) = 39.5 + 0.18 cos [15 (t-0.23)]. The presence of a 24 h rhythm of rectal t degree in lambs kept under nycthemeral conditions, and its persistence in lambs kept under constant light suggests that the rhythm of rectal temperature observed in the newborn lamb is a true circadian rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)     

Determining optimal clothing ensembles based on weather forecasts,with particular reference to outdoor winter military activities

Military and civil defense personnel are often involved in complex activities in a variety of outdoor environments. The choice of appropriate clothing ensembles represents an important strategy to establish the success of a military mission. The main aim of this study was to compare the known clothing insulation of the garment ensembles worn by soldiers during two winter outdoor field trials (hike and guard duty) with the estimated optimal clothing thermal insulations recommended to maintain thermoneutrality, assessed by using two different biometeorological procedures. The overall aim was to assess the applicability of such biometeorological procedures to weather forecast systems, thereby developing a comprehensive biometeorological tool for military operational forecast purposes. Military trials were carried out during winter 2006 in Pokljuka (Slovenia) by Slovene Armed Forces personnel. Gastrointestinal temperature, heart rate and environmental parameters were measured with portable data acquisition systems. The thermal characteristics of the clothing ensembles worn by the soldiers, namely thermal resistance, were determined with a sweating thermal manikin. Results showed that the clothing ensemble worn by the military was appropriate during guard duty but generally inappropriate during the hike. A general under-estimation of the biometeorological forecast model in predicting the optimal clothing insulation value was observed and an additional post-processing calibration might further improve forecast accuracy. This study represents the first step in the development of a comprehensive personalized biometeorological forecast system aimed at improving recommendations regarding the optimal thermal insulation of military garment ensembles for winter activities.     

The importance of aerobic fitness in determining tolerance to uncompensable heat stress

When protective clothing is worn that restricts evaporative heat loss, it is not valid to assume that the higher sweat rates associated with improvements in aerobic fitness will increase heat tolerance. An initial study compared thermoregulatory and cardiovascular responses to both compensable and uncompensable heat stress before and after 8 weeks of endurance training in previously sedentary males. Despite a 15% improvement in VO2peak, and lower heart rates and rectal temperature (T(re)) responses while wearing combat clothing, no changes were noted when subjects wore a protective clothing ensemble. Tolerance times were unchanged at approximately 50 min. A subsequent short-term training model that used daily 1-h exercise sessions for 2 weeks also failed to show any benefit when the protective clothing was worn in the heat. Cross-sectional comparisons between groups of high and low aerobic fitness, however, have revealed that a high aerobic fitness is associated with extended tolerance time when the protective clothing is worn. The longer tolerance time is a function of both a lower starting T(re) and a higher T(re) tolerated at exhaustion. Improvements in cardiovascular function with long-term training may allow higher core temperatures to be reached prior to exhaustion. Conversely, elevations in core temperature that occur with normal training sessions may familiarize the more fit subjects to the discomforts of exercise in the heat. Other factors such as differences in body fatness may account for a faster increase in tissue temperature at a given metabolic rate for less fit individuals.     

First investigations to refine video-based IR thermography as a non-invasive tool to monitor the body temperature of calves

In this study, a video-based infrared camera (IRC) was investigated as a tool to monitor the body temperature of calves. Body surface temperatures were measured contactless using videos from an IRC fixed at a certain location in the calf feeder. The body surface temperatures were analysed retrospectively at three larger areas: the head area (in front of the forehead), the body area (behind forehead) and the area of the entire animal. The rectal temperature served as a reference temperature and was measured with a digital thermometer at the corresponding time point. A total of nine calves (Holstein-Friesians, 8 to 35 weeks old) were examined. The average maximum temperatures of the area of the entire animal (mean±SD: 37.66±0.90°C) and the head area (37.64±0.86°C) were always higher than that of the body area (36.75±1.06°C). The temperatures of the head area and of the entire animal were very similar. However, the maximum temperatures as measured using IRC increased with an increase in calf rectal temperature. The maximum temperatures of each video picture for the entire visible body area of the calves appeared to be sufficient to measure the superficial body temperature. The advantage of the video-based IRC over conventional IR single-picture cameras is that more than one picture per animal can be analysed in a short period of time. This technique provides more data for analysis. Thus, this system shows potential as an indicator for continuous temperature measurements in calves.