Ratings Of Thermal Sensation Research Articles

Thermoregulatory demands of épée fencing during competition

ABSTRACT The International Olympic Committee recently introduced a consensus statement on recommendations for outdoor sports in the heat. However, indoor sports such as fencing whereby athletes are required to wear full body protective clothing when competing have received no recommendations. Such scenarios could cause high thermoregulatory demands particularly as competition progresses into latter rounds (direct elimination; DE). Therefore, the aim of this study was to determine the thermoregulatory responses of épée fencing across different phases of competition (Poule and DE). Seven well-trained fencers competed in a simulated competition comprising of seven Poule and seven DE fights. Gastrointestinal temperature (Tgast), skin temperature (Tskin), mask temperature (Tmask), heart rate (HR), thermal sensation, differentiated ratings of perceived exertion (RPE), and movement characteristics were collected for all fights. There was a moderate thermoregulatory demand during Poule rounds shown by post-fight Tgast (38.1 ± 0.4°C), Tskin (34.4 ± 0.7°C), and thermal sensation ratings (6 ± 1). A greater thermoregulatory and perceptual demand observed during DE rounds evidenced by Tgast (38.7 ± 0.3°C post fight), Tskin (35.1 ± 0.7°C), thermal sensation (7 ± 1), increases in Tmask across DE rounds (~1.1°C), and RPE (~15). Furthermore, a significant (p < 0.05) reduction in distance covered from DE 1 to DE 7 suggests a thermoregulatory based impact on performance. This is the first study demonstrating the thermoregulatory demands of épée fencing, highlighting the need to develop heat exertion guidelines within fencing.

The effect of a combined cooling intervention on cognitive function in the heat during an intermittent running protocol.

Despite optimal cognitive function being essential for performance, there is a lack of research on the effectiveness of combined cooling interventions on team sport athlete's cognitive function when exercising in the heat. In a randomised, crossover design, 12 unacclimatised men (age: 22.3±3.0years, body mass: 73.4±5.1kg, height: 181.0±5.3cm and max: 51.2±9.5mL/kg/min) participated in a control (CON) and combined cooling trial (ice slurry and ice collar; COOL). A battery of cognitive tests were completed prior to, during (at half-time) and following a 90-min intermittent running protocol in the heat (33°C, 50% relative humidity (RH)). Perceptual and physiological measures were taken throughout the protocol. In CON, response times were quicker on the Stroop task complex level (p=0.002) and the visual search test complex level at full-time (p=0.014) compared to COOL. During COOL, response times were quicker at half-time on the Stroop task complex level (p=0.024) compared to CON. Lower rectal temperatures were seen during COOL (CON: 37.44±0.65°C and COOL: 37.28±0.68°C) as well as lower skin, neck and forehead temperatures (main effect of trial, all p<0.05). Lower ratings of thermal sensation and perceived exertion and enhanced thermal comfort were recorded during COOL (main effect of trial, all p<0.05). Whilst minimal differences in cognitive function were found when using the combined cooling intervention, the findings highlight a practical and effective strategy to improving many physiological and perceptual responses to intermittent exercise in the heat.

An evaluation of the effects of localised skin cooling on microvascular, inflammatory, structural, and perceptual responses to sustained mechanical loading of the sacrum: A study protocol.

This study protocol aims to investigate how localised cooling influences the skin's microvascular, inflammatory, structural, and perceptual tolerance to sustained mechanical loading at the sacrum, evaluating factors such as morphology, physiology, and perceptual responses. The protocol will be tested on individuals of different age, sex, skin tone and clinical status, using a repeated-measure design with three participants cohorts: i) young healthy (n = 35); ii) older healthy (n = 35); iii) spinal cord injured (SCI, n = 35). Participants will complete three testing sessions during which their sacrum will be mechanically loaded (60 mmHg; 45 min) and unloaded (20 min) with a custom-built thermal probe, causing pressure-induced ischemia and post-occlusive reactive hyperaemia. Testing sessions will differ by the probe's temperature, which will be set to either 38°C (no cooling), 24°C (mild cooling), or 16°C (strong cooling). We will measure skin blood flow (via Laser Doppler Flowmetry; 40 Hz); pro- and anti-inflammatory biomarkers in skin sebum (Sebutape); structural skin properties (Optical Coherence Tomography); and ratings of thermal sensation, comfort, and acceptance (Likert Scales); throughout the loading and unloading phases. Changes in post-occlusive reactive hyperaemia will be considered as the primary outcome and data will be analysed for the independent and interactive effects of stimuli's temperature and of participant group on within- and between-subject mean differences (and 95% Confidence Intervals) in peak hyperaemia, by means of a 2-way mixed model ANOVA (or Friedman). Regression models will also be developed to assess the relationship between absolute cooling temperatures and peak hyperaemia. Secondary outcomes will be within- and between-subject mean changes in biomarkers' expression, skin structural and perceptual responses. This analysis will help identifying physiological and perceptual thresholds for the protective effects of cooling from mechanically induced damage underlying the development of pressure ulcers in individuals varying in age and clinical status.

Living in Western Australia induces some physiological adaptations of seasonal acclimatisation in the surgical burns team

ABSTRACT Seasonal acclimatization is known to result in adaptations that can improve heat tolerance. Staff who operate on burn injuries are exposed to thermally stressful conditions and seasonal acclimatization may improve their thermoeffector responses during surgery. Therefore, the aim of this study was to assess the physiological and perceptual responses of staff who operate on burn injuries during summer and winter, to determine whether they become acclimatized to the heated operating theater. Eight staff members had physiological and perceptual responses compared during burn surgeries conducted in thermoneutral (CON: 24.1 ± 1.2°C, 45 ± 7% relative humidity [RH]) and heated (HOT: 31.3 ± 1.6°C, 44 ± 7% RH) operating theaters, in summer and winter. Physiological parameters that were assessed included core temperature, heart rate, total sweat loss, sweat rate, and urinary specific gravity. Perceptual responses included ratings of thermal sensation and comfort. In summer, CON compared to winter CON, baseline (85 ± 15 bpm VS 94 ± 18 bpm), mean (84 ± 16 bpm VS 93 ± 18 bpm), and peak HR (94 ± 17 bpm VS 105 ± 19 bpm) were lower (p < 0.05), whereas core temperature was not different between seasons in either condition (p > 0.05). In HOT, ratings of discomfort were higher in summer (15 ± 3) than winter (13 ± 3; p > 0.05), but ratings of thermal sensation and sweat rate were similar between seasons (p > 0.05). The surgical team in burns in Western Australia can obtain some of the physiological adaptations that result from seasonal acclimatization, but not all. That is most likely due to a lower than required amount of outdoor heat exposure in summer, to induce all physiological and perceptual adaptations.

Influence Of Tyrosine On Body Temperature And Perceptual Responses To Cold Water Immersion In Military Cold-weather Medicine Trainees

Cold stress often results in physical and cognitive performance decrements. Tyrosine supplementation may attenuate deficits due to its ability to synthesize and maintain appropriate levels of brain catecholamines. However, the influence of tyrosine on physiological and perceptual responses to cold water immersion has not been reported. PURPOSE: Determine the influence of tyrosine supplementation on physiological and perceptual responses to cold water immersion during a military field training exercise. METHODS: Military personnel (n = 14; age: 26 ± 7 y; body fat: 20.1 ± 8.5%) completed a field training exercise that included a 10-min, head-out, cold water (1.5 °C) immersion in cold air (4 °C). In a randomized, double-blind design, prior to immersion (range 30-120 min), participants ingested either a food bar with 150 mg/kg of body weight of supplemental tyrosine (TYR; n = 7) or placebo (PLA; n = 7). TYR and PLA food bars were matched for taste, texture, and color. Prior to, during, and after immersion, participants’ heart rate (HR), hand temperature (Thand), skin temperature (Tsk), and core temperature (Tc) were measured while ratings of thermal sensation (TS) and shivering sensation (SS) were obtained throughout the exercise. Comparisons between TYR and PLA were made using an analysis of variance with significance set at p < 0.05. RESULTS: Oral tyrosine supplementation improved Tc maintenance, with the greatest difference between TYR and PLA evidenced at 10 min after completion of immersion (TYR: 36.7 ± 0.5, PLA 35.7 ± 0.8 °C, p < 0.05). No differences were observed between TYR and PLA for HR (p = 0.284), Thand (p = 0.693), Tsk (p = 0.947), TS (p = 0.262), or SS (p = 0.068). CONCLUSION: Findings suggest that tyrosine supplementation improved Tc maintenance in response to cold water immersion. However, tyrosine supplementation had minimal influence on thermal perceptions and did not modify HR or Tsk prior to, during, or after immersion. The conservation of core temperature associated with tyrosine supplementation is consistent with other reports, and its mechanisms of action warrant further investigation. This information is critical for deeper understanding of the complex physiological responses to environmental extremes in order to optimize strategies to sustain or enhance human performance in cold environments.

The influence of structure on the thermal properties of sleeping bags

PurposeTo understand the thermal insulation of four common structures of sleeping bags and factors influencing the thermal insulation as well as the thermal comfort of people who use four kinds of sleeping bag structures.Design/methodology/approachFour samples corresponding to four common sleeping bag structures were made and their thermal properties were investigated through a combination of objective instrument measurement and subjective human subject tests.FindingsThe porosity of the samples and the length of the interlining had a main impact on the thermal resistances of the four sleeping bag structures. The thermal sensation ratings and the thermal resistances had good consistency. There was a strong correlation between human physiological parameters and thermal sensation evaluation. The male and female have significant differences in thermal sensation of different structures of sleeping bags.Originality/valueInstrument measurement and human subject tests were combined to study the thermal properties of sleeping bag structures, which had little attention in the past in research fields.

Investigating the relation between electroencephalogram, thermal comfort, and cognitive performance in neutral to hot indoor environment.

The relation between electroencephalogram signals, thermal comfort, and cognitive performance in neutral to hot indoor environment was investigated. The experiments were carried out at four temperatures: 26ºC, 30ºC, 33ºC, and 37ºC, and two relative humidity levels: 50% and 70%. Thirty-two subjects were exposed for 175min. The electroencephalogram signals were measured for 30min 25min after the onset of exposure while the recruited subjects performed neurobehavioral tests and rated their thermal comfort. The relative power of electroencephalogram signals has a significant correlation with thermal comfort and performance of neurobehavioral tests. The ratings of acceptability of thermal environment and thermal comfort, the speed, accuracy, and PI of completing the tests are negatively correlated with the relative power of δ-band, but positively correlated with θ-band, α-band, and β-band. The ratings of thermal sensation have a better correlation with the above four bands, but the correlation trend is opposite. A linear relation was found between electroencephalogram signals and the speed. The results showed that the relative power of P7 channel located in the occipital lobe is the most suitable as a single electroencephalogram channel to reflect joint thermal comfort and cognitive performance at high temperatures, especially its α-band.

Comparison of the effect of post-exercise cooling with ice slurry ingestion between males and females.

This study aimed to compare the effects of ice slurry ingestion on post-exercise cooling in males and females. Twenty-four healthy adults (male n=12; body weight [BW], 65.8±10.3kg; female, n=12; BW, 58.2±10.0kg) participated in this study. Participants ingested 7.5g/kg of either ice slurry at -1°C (ICE) or control fluid at 20°C (CON) during recovery after cycling at 55% VO2max until the rectal temperature reached 38.5°C or exhaustion in a hot environment (controlled at 38°C, 40% relative humidity). Rectal (Tre) and skin (Tsk) temperature, ratings of thermal sensation (TS), thermal comfort (TC), heart rate (HR), mean arterial pressure (MAP), and whole body sweat loss (WBSL) were measured 60min after exercise. Ice slurry ingestion reduced Tre and TS and improved post-exercise hypotension only in females (p<0.05). In comparison, males did not receive cooling effect from post- exercise cooling with ice slurry ingestion. WBSL tended to be lower in ICE than CON in males (ICE, 454.3±172.3g; CON, 539.7±157.2g; p=0.065). In conclusion, sex differences were observed in the effects of post-exercise cooling with ice slurry ingestion.

Evaluation of individual thermal sensation at raised indoor temperatures based on skin temperature

In this study, we further investigate whether skin temperature can also assess individual thermal sensation as an effective physiological index while previous studies did not draw broadly generalizable conclusions at high temperature. The climate-controlled experiments include five temperature levels of 26, 30, 33, 37 and 39 °C, two relative humidity levels of 50% and 70%, and two activity levels with light and moderate and in which the estimated average metabolic rate were respectively 58 W/m2 and 165 W/m2. A total of 136 healthy subjects who lived in hot-humid climate for a long time participated in these experiments. During the experiments, the ratings of thermal sensation, comfort and acceptability were documented, local skin temperatures were continuously monitored, and five mean skin temperatures were calculated. Using Fisher discriminant analysis to model thermal sensation from skin temperature, then obtaining the thresholds of local and mean skin temperatures corresponding to different thermal sensation categories, and finally verifying the accuracy of the models assessment. The results show that the skin temperature can also predict thermal sensation at high temperatures of 30–39 °C beyond the range of normal temperatures. The proposed evaluation models show a high accuracy to predict the “hot/very hot” category, and up to 93% accuracy of predicting thermal sensation from wrist skin temperature. Additionally, thermal adaptation to high temperature and humidity can affect the prediction accuracy of “hot/very hot” category from skin temperature. The results of this study provide an important basis for early warning when human's safety risk occurs under high temperatures.

Differences between sexes in thermoregulatory responses and exercise time during endurance exercise in a hot environment following pre-cooling with ice slurry ingestion.

This study aimed to examine differences between sexes in thermoregulatory responses and exercise time after ice slurry ingestion in a hot environment. Twenty-four healthy adults (male n=12, body weight (BW)=65.8±10.3; female n=12, BW=58.2±10.0) ingested 7.5g/kg of either ice slurry at -1°C (ICE) or control water at 20°C (CON) before cycling at 55%VO2 max in a hot environment (controlled at 38°C, 40% relative humidity). Rectal (Tre) and skin (Tsk) temperature, heart rate, sweat rate, respiratory gases, ratings of thermal sensation (TS), thermal comfort (TC), and rating of perceived exertion (RPE) were measured. Ice slurry did not improve exercise time in both sexes despite Tre was significantly lower in ICE than CON in both sexes. Tre, Tsk, HR, sweat rate and TS did not differ between sexes. TC and RPE in ICE were significantly higher during exercise in males than in females. In conclusion, there were no sex differences in the effects of pre-cooling with ice slurry ingestion; however, pre-cooling with ice slurry may be more effective in mitigating ratings of TC and RPE in females than males.

Hand and torso pre-cooling does not enhance subsequent high-intensity cycling or cognitive performance in heat

ABSTRACT The purpose of this study was to compare the separate and combined effects of two practical cooling methods (hand and torso) used prior to exercise on subsequent high-intensity cycling performance in heat. Ten trained male cyclists (V̇O2peak: 65.7 ± 10.7 ml.kg−1.min−1) performed four experimental trials (randomised within-subjects design) involving 30-min of pre-cooling (20-min seated; PRE-COOL, 10 min warm-up; PRE-COOL+WUP), while using a: (1) hand-cooling glove (CG); (2) cooling jacket (CJ); (3) both CG and CJ (CG+J); or (4) no-cooling (NC) control, followed by a cycling race simulation protocol (all performed in 35.0 ± 0.6°C and 56.6 ± 4.5% RH). During the 30-min of pre-cooling, no reductions in core (Tc) or mean skin temperature (Tsk) occurred; however, Tsk remained lower in the CJ and CG+J trials compared to NC and CG (p = 0.002–0.040, d= 0.55–1.01). Thermal sensation ratings also indicated that participants felt “hotter” during NC compared to all other trials during both PRE-COOL and PRE-COOL+WUP (p = 0.001–0.015, d= 1.0–2.19), plus the early stages of exercise (sets 1–2; p = 0.005–0.050, d= 0.56–1.22). Following cooling, no differences were found for absolute Tc and Tsk responses between trials over the entire exercise protocol (p > 0.05). Exercise and cognitive (working memory) performance also did not differ between trials (p = 0.843); however, cognitive performance improved over time in all trials (p < 0.001). In summary, pre-cooling (20-min seated and 10-min warm-up) in heat did not improve subsequent high-intensity cycling performance, cognitive responses and associated thermoregulatory strain (Tc and Tsk) compared to control.

Could wearing motorcycle protective clothing compromise rider safety in hot weather?

Motorcycle protective clothing (PPE) effectively reduces the risk of injury in crashes, however in hot conditions many motorcyclists ride unprotected. Recent work found available motorcycle PPE to be thermally inefficient in hot weather with potential to cause significant thermal strain under average Australian summer conditions. The current study investigated the potential for the cognitive and psychophysical concomitants of thermal strain to compromise reaction times, mood and fatigue with potential consequences for motorcyclists’ safety. MethodVolunteers wearing motorcycle PPE participated in a 90 min trial (cycling 30 W) in 35 °C, 40%RH with overhead radiant heaters and a fan to simulate wind speed. Heart rate, core and skin temperature were recorded continuously. Reaction time and subjective ratings of thermal sensation and comfort, workload and mood were recorded at baseline, during rest breaks at 25 min intervals and on completion of the trail. Repeated measures analysis assessed each participant’s performance against their own baseline. ResultsCore temperatures increased by 2 °C (p < .0001), skin temperatures (3 °C, (p < .0001) and heart rates (66bpm, p < .0001). Reaction times fluctuated 36 ms 8% (p < .0001) over the trial. Subjective workload increased 68% (p = 0.001) and mood deteriorated 33 points (p < .0001) including feeling less alert (p = <.0001), contented (p = 0.001) and calm (p = 0.0004). Multivariate repeated measures analysis found significant associations between core temperature and workload (p = 0.01), mood (p = 0.001) and reaction time (<.0001). Skin temperature and workload (p = 0.02), mood (p = 0.01) and reaction time (<.0001). Subjective ratings of temperature sensation and wetness discomfort were associated respectively with increased workload (p = 0.0001, p = 0.004), mood change (p < .0001, p = 0.04) and reaction time (p < .0001, p < .0001). ConclusionsThe physiological impact of wearing thermally inefficient motorcycle PPE in hot conditions could impair motorcyclists cognitive and psychophysical functioning and, potentially, their riding performance and safety.These outcomes indicate an urgent need for manufacturers to develop motorcycle PPE that is effective and suitable for use, in hot conditions.

Broadening human thermal comfort range based on short-term heat acclimation

Elevating indoor temperature set-points can reduce cooling energy use. Short-term heat acclimation (HA), the artificially induced adaptation developed in three consecutive days, is an effective method to increase the occupants' acceptance to hot environments. However, the quantitative study on the effects of short-term HA on thermal comfort is lacking. To this end, simulated experiments were conducted in a climate chamber to test the difference of subjects' thermal comfort before and after short-term HA. The subjects were instructed to do intermittent treadmill exercise under hot conditions to reach a HA state. During the trials, core temperature, ratings of perceived exertion (RPE), and ratings of thermal sensation (RTS) were measured. Perceptual strain index (PeSI) was used to assess the effect of short-term HA. The results showed that short-term HA could improve subjects’ adaptability to warmer environments without sacrificing thermal comfort. Furthermore, a HA zone was defined based on the predicted percentage of dissatisfied (PPD) of 10%. The upper limit of the HA zone was 2.1 °C higher than that of the summer thermal comfort zone in ASHRAE Standard 55–2017. This finding suggests that a higher temperature set-point could be considered into the control of air-conditioning systems, contributing to building energy conservation.

Assessment of brain mechanisms involved in the processes of thermal sensation, pleasantness/unpleasantness, and evaluation

The conscious perception of thermal stimuli is divided into two categories: thermal sensation (i.e., discriminative component) and pleasantness/unpleasantness (i.e., hedonic component). There have been very few studies which clearly dissociated the two components. The aim of the present study was 1) to identify brain regions involved in perception of thermal stimuli per se, dissociating those related to the two components, and additionally 2) to examine brain regions of the explicit evaluation processes for the two components. Sixteen participants received local thermal stimuli of either 41.5 °C or 18.0 °C during whole-body thermal stimuli of 47.0 °C, 32.0 °C, or 17.0 °C. The local stimuli were delivered to the right forearm with the Peltier device. The whole-body stimuli delivered through a water-perfusion suit was aimed to modulate thermal pleasantness/unpleasantness to the local stimulus. The local stimulation at the same temperature was conducted five times with 30-s intervals. Brain activation was assessed by functional magnetic resonance imaging (fMRI), and the participants were asked to report their ratings of thermal sensation and pleasantness/unpleasantness following the cessation of each local stimulus. Local thermal stimulation activated specific brain regions such as the anterior cingulate cortex, insula, and inferior parietal lobe, irrespective of the temperature of local and whole-body stimuli; however, no specific activation for hot or cold sensation was observed. Different brain regions were associated with pleasantness and unpleasantness; the caudate nucleus and frontal regions for pleasantness, and the medial frontal and anterior cingulate cortex for unpleasantness. In addition, the explicit evaluation process for the discriminative and hedonic components immediately following the cessation of local stimulus involved different brain regions; the medial prefrontal cortex extending to the anterior cingulate cortex, insula, middle frontal cortex, and parietal lobes during the explicit evaluation of thermal sensation, and the medial prefrontal cortex, posterior cingulate cortex, and inferior parietal lobes during that of pleasantness/unpleasantness.

PO-246 Effects of Different Methods of Precooling on Sub-maximal Intensity Exercise in Heat and High Humidity

Objective This study aimed to investigate the influence of using different precooling measures on the capacity of competition and the exercise performance in hot and humidity environment. The most effectual means of precooling will be recommended to help coaches and athletes to improve the ability and performance in training and matches&#x0D; Methods Ten male football (Rugby) players who came from the rugby team totally completed four experimental conditions in hot/humid conditions (38℃, 50% humidity). Initially, a 30-min precooling period consisting of either nothing to control (CONT, C); wearing cooling vest (4℃, V); ingesting of ice beverage (2.3 ml /kg of 4℃, I); or the mix method of combination of V and I (V+I, M). Following this, sub-maximal exercise (80% VO2max) of treadmill test occurred, until athletes exhausted&#x0D; Results The running distance of M and V and I have a significant increase (P≤0.05) than CONT. The peak oxygen uptake of exhaustion was no significant difference between each other. After exercise, the change rate of heart rate ratio of M compared with CONT has a very significant decrease (P≤0.01). The core temperature of M and CONT has a significant increase (P≤0.05) in comparison. The surface temperature of I and M and V comparison with CONT has a very significant increase (P≤0.01). When participants exhaust, the RPE of M in comparison with CONT had significantly lower (P≤0.05). The RPB and the rating of thermal sensation of each condition were no significant difference. After exercise, the blood lactic concentration of each ones was no significant difference&#x0D; Conclusions In hot and humidity condition, precooling has a promoting effect on the sub-maximal exercise. Precooling measures could improve the exercise performance and maintain the stability of functional status and physiology, especially the mix method.&#x0D;

Thermal Sensations during a Partial-Body Cryostimulation Exposure in Elite Basketball Players.

Partial-body cryostimulation is used to improve recovery after exercise, especially during competitions or heavy training; however, a limited number of studies have been conducted with international-level athletes in situ during competitions. This study was undertaken to assess the thermal sensation ratings during 3 min of cold exposure (at –130°C) in 24 international-level athletes during the European Basketball Championship. The mean thermal sensation score, measured using a perceptive scale, increased significantly (p < 0.05) during partial-body cryostimulation exposure in athletes from 3.0 ± 1.7 at 30 s to 5.7 ± 2.3 at 3 min (maximal observed value = 10.0). The mean value of 5.7 is considered a “cold” sensation on the scale (ranging from 0 = neutral sensation to 10 = very cold). However, we observed a large inter-individual variation in the perceived thermal sensations. The body mass index was significantly and negatively correlated with the thermal sensation value after 2 min 30 s and 3 min of exposure in females (r = –0.61, n = 13, p < 0.05; r = –0.56, n = 13, p = 0.054, respectively). Three participants reported high perceived thermal sensation after 30 s of exposure and their cold-induced discomfort worsened as the exposure continued. In conclusion, a 3-min exposure is globally well tolerated by athletes and can be used during a heavy competition period and/or during a training period. However, special attention should be given to female athletes with a low body mass index as they seem to be much more sensitive to cold.

Developing a continuous graphical index to assess heat strain in extremely hot environments

Extremely hot environments are common in industrial buildings, which impose thermal risks on the homeostasis of the human body. Thermal protective clothing (TPC) also places physical and thermal burdens on workers. In order to ensure workers' health and work efficiency, a continuous graphical index is developed in this paper to assess heat strain in extremely hot environments, avoiding hard measurements of physiological parameters. To study human interaction with the indoor thermal environment, a climate chamber was constructed to simulate extremely hot environments. Twenty male sports majors were asked to perform intermittent treadmill exercise while wearing TPC. During the human trials, rectal temperature, heart rate, hand grip strength, ratings of perceived exertion, and ratings of thermal sensation were measured. The results of a two-way repeated analysis of variance revealed that the perceptual strain index (PeSI) can reflect influences of different work intensities and dry bulb temperatures on human heat tolerance. The results of a regression analysis revealed a strong correlation between the physiological strain index (PSI) and the PeSI. In addition, the results also revealed a strong correlation between the PSI and work efficiency. By fitting the continuous function, the proposed index defined the comfort limit, efficiency limit, and safety limit for manual labourers wearing TPC. Therefore, the proposed index derived from the findings can be used to assess heat strain and work efficiency of workers in extremely hot environments.

Temperate-Water Immersion as a Treatment for Hyperthermic Humans Wearing American Football Uniforms.

Cold-water immersion (CWI; 10°C) can effectively reduce body core temperature even if a hyperthermic human is wearing a full American football uniform (PADS) during treatment. Temperate-water immersion (TWI; 21°C) may be an effective alternative to CWI if resources for the latter (eg, ice) are unavailable. To measure rectal temperature (Trec) cooling rates, thermal sensation, and Environmental Symptoms Questionnaire (ESQ) scores of participants wearing PADS or shorts, undergarments, and socks (NOpads) before, during, and after TWI. Crossover study. Laboratory. Thirteen physically active, unacclimatized men (age = 22 ± 2 years, height = 182.3 ± 5.2 cm, mass = 82.5 ± 13.4 kg, body fat = 10% ± 4%, body surface area = 2.04 ± 0.16 m2). Participants exercised in the heat (40°C, 50% relative humidity) on 2 days while wearing PADS until Trec reached 39.5°C. Participants then underwent TWI while wearing either NOpads or PADS until Trec reached 38°C. Thermal sensation and ESQ responses were collected at various times before and after exercise. Temperate-water immersion duration (minutes), Trec cooling rates (°C/min), thermal sensation, and ESQ scores. Participants had similar exercise times (NOpads = 38.1 ± 8.1 minutes, PADS = 38.1 ± 8.5 minutes), hypohydration levels (NOpads = 1.1% ± 0.2%, PADS = 1.2% ± 0.2%), and thermal sensation ratings (NOpads = 7.1 ± 0.4, PADS = 7.3 ± 0.4) before TWI. Rectal temperature cooling rates were similar between conditions (NOpads = 0.12°C/min ± 0.05°C/min, PADS = 0.13°C/min ± 0.05°C/min; t12 = 0.82, P = .79). Thermal sensation and ESQ scores were unremarkable between conditions over time. Temperate-water immersion produced acceptable (ie, >0.08°C/min), though not ideal, cooling rates regardless of whether PADS or NOpads were worn. If a football uniform is difficult to remove or the patient is noncompliant, clinicians should begin water-immersion treatment with the athlete fully equipped. Clinicians should strive to use CWI to treat severe hyperthermia, but when CWI is not feasible, TWI should be the next treatment option because its cooling rate was higher than the rates of other common modalities (eg, ice packs, fanning).

Pre-cooling with intermittent ice ingestion lowers the core temperature in a hot environment as compared with the ingestion of a single bolus

The timing in which ice is ingested may be important for optimizing its success. However, the effects of differences in the timing of ice ingestion has not been studied in resting participants. Therefore, the purpose of this study was to investigate the effects of differences in the timing of ice ingestion on rectal temperature (Tre) and rating of perceptual sensation in a hot environment. Seven males ingested 1.25gkg−1 of crushed ice (ICE1.25: 0.5°C) or cold water (CON: 4°C) every 5min for 30min, or were given 7.5gkgBM−1 of crushed ice (ICE7.5) to consume for 30min in a hot environment (35°C, 30% relative humidity). The participants then remained at rest for 1h. As physiological indices, Tre, body mass and urine specific gravity were measured. Rating of thermal sensation was measured at 5-min intervals throughout the experiment. ICE1.25 continued to decrease Tre until approximately 50min, and resulted in a greater reduction in Tre (−0.56±0.20°C) than ICE7.5 (−0.41±0.14°C). Tre was reduced from 40 to 75min by ICE1.25, which is a significant reduction in comparison to ICE7.5 (p<.05). Mean RTS with ICE1.25 at 50–65min was significantly lower than that with ICE7.5 (p<.05). These results suggest that pre-cooling with intermittent ice ingestion is a more effective strategy both for lowering the Tre and for the rating of thermal sensation.

Necessity of Removing American Football Uniforms From Humans With Hyperthermia Before Cold-Water Immersion.

The National Athletic Trainers' Association and the American College of Sports Medicine have recommended removing American football uniforms from athletes with exertional heat stroke before cold-water immersion (CWI) based on the assumption that the uniform impedes rectal temperature (T(rec)) cooling. Few experimental data exist to verify or disprove this assumption and the recommendations. To compare CWI durations, T(rec) cooling rates, thermal sensation, intensity of environmental symptoms, and onset of shivering when hyperthermic participants wore football uniforms during CWI or removed the uniforms immediately before CWI. Crossover study. Laboratory. Eighteen hydrated, physically active men (age = 22 ± 2 years, height = 182.5 ± 6.1 cm, mass = 85.4 ± 13.4 kg, body fat = 11% ± 5%, body surface area = 2.1 ± 0.2 m(2)) volunteered. On 2 days, participants exercised in the heat (approximately 40°C, approximately 40% relative humidity) while wearing a full American football uniform (shoes; crew socks; undergarments; shorts; game pants; undershirt; shoulder pads; jersey; helmet; and padding over the thighs, knees, hips, and tailbone [PADS]) until T(rec) reached 39.5°C. Next, participants immersed themselves in water that was approximately 10°C while wearing either undergarments, shorts, and crew socks (NOpads) or PADS without shoes until Trec reached 38°C. The CWI duration (minutes) and T(rec) cooling rates (°C/min). Participants had similar exercise times (NOpads = 40.8 ± 4.9 minutes, PADS = 43.2 ± 4.1 minutes; t(17) = 2.0, P = .10), hypohydration levels (NOpads = 1.5% ± 0.3%, PADS = 1.6% ± 0.4%; t(17) = 1.3, P = .22), and thermal-sensation ratings (NOpads = 7.2 ± 0.3, PADS = 7.1 ± 0.5; P > .05) before CWI. The CWI duration (median [interquartile range]; NOpads = 6.0 [5.4] minutes, PADS = 7.3 [9.8] minutes; z = 2.3, P = .01) and T(rec) cooling rates (NOpads = 0.28°C/min ± 0.14°C/min, PADS = 0.21°C/min ± 0.11°C/min; t(17) = 2.2, P = .02) differed between uniform conditions. Whereas participants cooled faster in NOpads, we still considered the PADS cooling rate to be acceptable (ie, >0.16°C/min). Therefore, if clinicians experience difficulty removing PADS or CWI treatment is delayed, they may immerse fully equipped hyperthermic football players in CWI and maintain acceptable T(rec) cooling rates. Otherwise, PADS should be removed preimmersion to ensure faster body core temperature cooling.