Search

People perceive thermal sensation differently despite the same temperature value of thermal comfort index depending on various factors such as climate, culture, and physiological characteristics. The use of the thermal comfort index without optimization may lead to biases in assessment of thermal stress and sensation. This study aims to derive the perceived temperature (PT) ranges of thermal sensation levels related to heat stress for Koreans. The experiments were designed using a controlled environmental chamber to derive the PT ranges and were performed with subjects who are residents of Seoul, South Korea. The experiments were carried out in the summers of 2017 and 2018, and the thermal sensation votes were surveyed from 19 subjects whose mean age, height, weight, and body mass index were 22.5 years, 171 cm, 72 kg, and 23 kg⋅m−2, respectively. The derived PT ranges for Koreans led to a better performance than the reference PT ranges for Germans based on the results of validation. The thresholds of ‘Warm,’ ‘Hot,’ and ‘Very hot’ thermal sensation classes for Koreans were 28 °C, 36 °C, and 43 °C, respectively: higher than those for Germans. The results indicate that Koreans may have higher heat resistance or lower heat sensitivity than Germans.

Background: While increased face mask use has helped reduce COVID-19 transmission, there have been concerns about its influence on thermoregulation during exercise in the heat, but consistent, evidence-based recommendations are lacking. Hypothesis: No physiological differences would exist during low-to-moderate exercise intensity in the heat between trials with and without face masks, but perceptual sensations could vary. Study Design: Crossover study. Level of Evidence: Level 2. Methods: Twelve physically active participants (8 male, 4 female; age = 24 ± 3 years) completed 4 face mask trials and 1 control trial (no mask) in the heat (32.3°C ± 0.04°C; 54.4% ± 0.7% relative humidity [RH]). The protocol was 60 minutes of walking and jogging between 35% and 60% of relative VO2max. Rectal temperature (Trec), heart rate (HR), temperature and humidity inside and outside of the face mask (Tmicro_in, Tmicro_out, RHmicro_in, RHmicro_out) and perceptual variables (rating of perceived exertion (RPE), thermal sensation, thirst sensation, fatigue level, and overall breathing discomfort) were monitored throughout all trials. Results: Mean Trec and HR increased at 30- and 60-minute time points compared with 0-minute time points, but no difference existed between face mask trials and control trials ( P > 0.05). Mean Tmicro_in, RHmicro_in, and humidity difference inside and outside of the face mask (ΔRHmicro) were significantly different between face mask trials ( P < 0.05). There was no significant difference in perceptual variables between face mask trials and control trials ( P > 0.05), except overall breathing discomfort ( P < 0.01). Higher RHmicro_in, RPE, and thermal sensation significantly predicted higher overall breathing discomfort ( r2 = 0.418; P < 0.01). Conclusion: Face mask use during 60 minutes of low-to-moderate exercise intensity in the heat did not significantly affect Trec or HR. Although face mask use may affect overall breathing discomfort due to the changes in the face mask microenvironment, face mask use itself did not cause an increase in whole body thermal stress. Clinical Relevance: Face mask use is feasible and safe during exercise in the heat, at low-to-moderate exercise intensities, for physically active, healthy individuals.

Assessing the adaptation of rectal temperature (Trec) is critical following heat acclimatization (HAz) and heat acclimation (HA) because it is associated with exercise performance and safety; however, more feasible and valid methods need to be identified. The purpose of this study was to predict adaptations in Trec from heart rate (HR), sweat rate (SR), and thermal sensation (TS) using predictive modeling techniques. Twenty-five male endurance athletes (age, 36 ± 12 y; VO2max, 57.5 ± 7.0 mL⋅kg−1⋅min−1) completed three trials consisting of 60 min running at 59.3 ± 1.7% vVO2max in a hot environment. During trials, the highest HR and TS, SR, and Trec at the end of trials were recorded. Following a baseline trial, participants performed HAz followed by a post-HAz trial and then completed five days HA, followed by a post-HA trial. A decision tree indicated cut-points of HR (0.3 L·h−1), and TS (≤−0.5) to predict lower Trec. When two or three variables met cut-points, the probability of accuracy of showing lower Trec was 95.7%. Greater adaptations in Trec were observed when two or three variables met cut-points (−0.71 ± 0.50 °C) compared to one (−0.13 ± 0.36 °C, p < 0.001) or zero (0.0 3 ± 0.38 °C, p < 0.001). Specificity was 0.96 when two or three variables met cut-points to predict lower Trec. These results suggest using heart rate, sweat rate, and thermal sensation adaptations to indicate that the adaptations in Trec is beneficial following heat adaptations, especially in field settings, as a practical and noninvasive method.

Although the life expectancy of women is over 80 years in many countries, oral sensation has scarcely been compared between adults ≥ 80 years and younger age groups. The purpose of this study was to clarify age-related changes in oral sensation throughout adulthood. After exclusion of individuals with factors that might have confounded somatosensory performance, 123 female participants were divided into four age groups: 20–39 years, 40–59 years, 60–79 years, and 80–96 years. Perceptions of tactile and thermal sensations were examined at points on the anterior and posterior palate, anterior and posterior tongue, lower labial-attached gingiva, lower lip, and buccal mucosa; two-point discrimination was examined only on the tongue. The tactile and two-point discrimination thresholds for the anterior and posterior tongue were significantly higher in the 80–96-year-old group than in any other age group (p

INTRODUCTION: Although evaporative heat loss capacity is reduced in burn-injured individuals with extensive skin grafts, the thermoregulatory strain due to a prior burn injury during exercise-heat stress may be negligible if the burn is located underneath protective clothing with low vapor permeability. PURPOSE: To test the hypothesis that heat strain during exercise in a hot-dry environment while wearing protective clothing would be similar with and without a simulated torso burn injury. METHODS: Ten healthy individuals (8M/2F) underwent three trials wearing: Uniform (combat uniform, tactical vest, and replica torso armor plates), Uniform with a 20% total body surface area (TBSA) simulated torso burn (Uniform + Burn), or shorts (and sports bra) only (Control). Exercise consisted of treadmill walking (5.3 km·h(–1); 3.7 ± 0.9% grade) for 60 min at a target heat production of 6.0 W·kg(−1) in 40.0 ± 0.1°C; 20.0 ± 0.6% relative humidity conditions. Measurements included rectal temperature, heart rate, rating of perceived exertion, and thermal sensation. RESULTS: No differences in rectal temperature (P ≥ 0.85), heart rate (P ≥ 0.99), thermal sensation (P ≥ 0.73), or rating of perceived exertion (P ≥ 0.13) occurred between Uniform + Burn and Uniform trials. In the Control trial, however, core temperature, heart rate, thermal sensation, and rating of perceived exertion were lower compared to the Uniform and Uniform + Burn trials (P ≤ 0.04 for all). CONCLUSION: A 20% TBSA simulated torso burn injury does not further exacerbate heat strain when wearing a combat uniform. These findings suggest that the physiological strain associated with torso burn injuries is not different from non-injured individuals when wearing protective clothing during an acute exercise-heat stress.

Purpose Given the pressing impact of global warming and its detrimental effect on the health of older populations, understanding age-related changes in thermoregulatory function is essential. Age differences in regional sweat distribution have been observed previously, but given the typically small measurement areas assessed, the development of whole body sweat maps for older individuals is required. Therefore, this study investigated age-related differences in regional sweat distribution in a hot environment (32 °C/50%RH) in young and older adults, using a body mapping approach. Methods Technical absorbent pads were applied to the skin of 14 young (age 24 ± 2 years) and 14 older (68 ± 5 years) males to measure regional sweat rate (RSR) at rest (30 min) and during exercise (30 min), at a fixed heat production (200 W m−2). Gastrointestinal (Tgi) and skin temperature (Tsk), heart rate, thermal sensation, and thermal comfort were also measured. Results Whole body sweat maps showed that despite equal heat production, healthy older males had significantly lower gross sweat loss (GSL) than the young and significantly lower RSR at almost all body regions at rest and at the hands, legs, ankles, and feet during exercise. The lower sweat loss in the older group coincided with a greater increase in Tgi and a consistently higher Tsk at the legs, despite subjectively feeling slightly cooler than younger individuals. Conclusion These findings support the evidence of age-related deterioration in both autonomic and subjective responses in the heat and highlight the lower extremities as the most affected body region.

Recently, studies suggest that the average indoor temperature is typically >30°C and that the maximum temperature can reach 37.5°C in hot-humid areas. However, the effects caused by increasing the humidity at high indoor temperatures are not clear. In this study, twelve female and twelve male subjects were exposed to different operative temperature (26.6, 30.6, and 37.4°C) and relative humidity (50% and 70%) in a climate chamber. Data concerning thermal sensation, perceived air quality, and Sick Building Syndrome (SBS) were collected during 190-min-long exposure to each thermal condition. Heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature were measured. It was found that increasing the relative humidity from 50% to 70% at 26 and 30°C had no significant effects on the physiological responses, thermal comfort, perceived air quality, or SBS symptoms of the subjects. However, when the temperature was elevated to 37°C, the heart rate, respiration rate, respiratory ventilation rate, mean skin temperature, and eardrum temperature increased significantly as a result of the increase in the relative humidity from 50% to 70%. The subjects felt hotter and more uncomfortable, and they found indoor air quality was more difficult to accept. The subjects are acclimatized to hot environments and more tolerant to heat. Therefore, the results are applicable to the acclimated people living in hot-humid climate.

We have tested the feasibility of thermal grills, a harmless method to induce pain. The thermal grills consist of interlaced tubes that are set at cool or warm temperatures, creating a painful “illusion” (no tissue injury is caused) in the brain when the cool and warm stimuli are presented collectively. Advancement in objective pain assessment research is limited because the gold standard, the self-reporting pain scale, is highly subjective and only works for alert and cooperative patients. However, the main difficulty for pain studies is the potential harm caused to participants. We have recruited 23 subjects in whom we induced electric pulses and thermal grill (TG) stimulation. The TG effectively induced three different levels of pain, as evidenced by the visual analog scale (VAS) provided by the subjects after each stimulus. Furthermore, objective physiological measurements based on electrodermal activity showed a significant increase in levels as stimulation level increased. We found that VAS was highly correlated with the TG stimulation level. The TG stimulation safely elicited pain levels up to 9 out of 10. The TG stimulation allows for extending studies of pain to ranges of pain in which other stimuli are harmful.

Cold sensitivity is common following nerve injuries in the upper extremity, but is less well studied in carpal tunnel syndrome (CTS). We investigated cold sensitivity in CTS and its effects on surgical outcome. A search of the Swedish National Registry for Hand Surgery (HAKIR) for open carpal tunnel releases (OCTR) from 2010-2016 identified 10,746 cases. Symptom severity questionnaires (HQ-8; HAKIR questionnaire 8, eight Likert-scale items scored 0-100, one item on cold sensitivity) and QuickDASH scores before and after surgery were collected. Patient mean age was 56 +/- SD 16 years, and 7,150/10,746 (67%) were women. Patients with severe cold sensitivity (defined as cold intolerance symptom severity score>70; n=951), scored significantly higher on QuickDASH at all time points compared to those with mild cold sensitivity (cold intolerance symptom severity scores Funding Agencies|Lund University; Kockska stiftelsen; Oscar II:s stipendium [V 2019/144]; Skane University Hospital; Region Skane; Diabetes Association in Malmo; Swedish Diabetes Foundation [DIA2016-117]

Multi-dimensions tactile displays, such as thermal and texture display, are desirable for enhancing perception while users experience virtual shopping such as touching a garment in virtual reality. Understanding the effect of one dimension on the other is fundamental for design of multi-dimensions tactile display. In this article, we report the effect of temperature on thresholds of voltage applied on an electrovibration tactile display. Three temperatures of the electrovibration tactile display at 18°C (cold), 30°C (neutral) and 38°C (warm) were considered in two experiments. In Experiment I, we measured the absolute thresholds of square wave voltage with 25 Hz, 140 Hz and 485 Hz. In Experiment II, we measured the amplitude discrimination thresholds of same voltage signals as in Experiment I. The results show that the absolute thresholds differed significantly between 18°C and 38°C for all the three frequencies. No significant difference in the absolute threshold was found between 18°C and 30°C, except for the 485 Hz voltage. The amplitude discrimination thresholds were essentially constant except for that of the 485 Hz voltage at 18°C, which were 17.11 Vpp and 16.86 Vpp larger than those at 30°C and 38°C, respectively.

Many children growing up in cities are spending less time outdoors to escape the heat. This is contributing to childhood obesity and the prospect of a range of diseases in adulthood. When landscape architects and urban designers use a human thermal comfort model to test their designs for children's comfort, they would have to use a model essentially designed to simulate healthy adults. Yet there are many differences between the body of a child and an adult. The aim of this paper was to modify the thermal comfort model COMFA into a children's energy budget model through the consideration of the heat exchange of a child. The energy budget of a child can be up to 21 W/m2 higher than adults in hot summertime conditions, and 26 W/m2 lower in cold conditions. The model was validated through field studies of 65 children (32 boys and 33 girls) aged from 7-12 years old in 9 days from March to June in 2019, in 68 different microclimates ranging from cool to hot. A 5-point thermal comfort scale of energy budget for children was created using multinomial logistic regression, which revealed that children have a different range of thermal acceptability than adults. The frequency distribution of the actual thermal sensation and the predicted thermal comfort was improved using the new scale. The actual thermal sensation responses from children and the predicted thermal sensation using the model was determined to be positively significantly related. The accuracy of the model was 93.26%. This study has provided an effective children's energy budget model to predict children's thermal comfort. Its application can contribute to the design of thermally comfortable children's outdoor play areas by landscape architects and urban designers.

This study examined the effectiveness of a field-type liquid cooling vest (LCV) worn underneath an impermeable protective suit on heat strain during walking. Eight men walked for 60 min at a moderate speed (3.0 km/h) wearing the suit in a warm environment (33°C, 60% relative humidity) without (control, CON) or with the LCV. A smaller increase in rectal temperature was recorded in participants in the LCV than in the CON condition (37.6 ± 0.1°C vs. 37.9 ± 0.1°C, p

In the hot climate of Saudi Arabia, people living year-round in air-conditioned spaces are likely to develop high expectations for homogeneity and cool temperatures, becoming potentially more sensitive if thermal conditions deviate from the comfort zone they expect. This paper presents the results from a field intervention investigating the association between participants’ thermal sensations with cognitive performance in a female university in Saudi Arabia. The climatic context plays a key role in choosing Saudi Arabia, whereas the total reliance on air-conditioners (AC) for cooling is believed to have significant effects on occupants’ perceptions of the comfort temperature. Results reveal discrepancies in the actual thermal sensations between the Saudi and non-Saudi participants which affected their performances. “Cool” and “Slightly Cool” sensations versus neutral were associated with significant lower percentage of errors and significant higher speed for all participants independently of any association with ethnicity and acclimatization. The estimates remained significant even after adjusting for ethnicity and the number of years spent in the country and the set temperature of AC at home. Implications of the study suggest a preference for staying cool when working independently of acclimatization status.

This study investigated whether hot water immersion (HWI) could heat acclimate athletes and improve intermittent running performance and perception of in-game running ability, during a competitive Australian Rules Football (ARF) season. Fifteen male semi-professional ARF athletes (Mean (SD); age: 22 (3) years, height: 182.3 (6.5) cm, mass: 80.5 (5.1) kg) completed either HWI (HEAT, N = 8, 13 (2) sessions, 322 (69) min exposure, 39.5 (0.3) °C) or acted as a control (CON, N = 7, no water immersion) over 6-weeks. Athletes completed a 30–15 Intermittent Fitness Test pre and post-intervention to assess intermittent running performance (VIFT), with perception of in-game running ability measured. Heat acclimation was determined via change in resting plasma volume, as well as physiological and perceptual responses during HWI. HEAT elicited large PV expansion (mean ± 90% CI: d = 1.03 ± 0.73), large decreases in heart rate (d = -0.89 ± 0.70), thermal sensation (d = -2.30 ± 1.15) and tympanic temperature (d = -1.18 ± 0.77). Large improvements in VIFT were seen in HEAT (d = 1.67 ± 0.93), with HEAT showing a greater improvement in VIFT when compared to CON (d = 0.81 ± 0.88). HEAT also showed greater belief that in-game running ability improved post-intervention (d = 2.15 ± 1.09) compared to CON. A 6-week HWI intervention can elicit heat acclimation, improve perception of in-game running ability, and potentially improve VIFT in semi-professional ARF athletes.

Thermal perception, including thermal sensation (TS), influences exercise performance in the heat. TS is a widely used measure and we examined the impact of initial TS (iTS) on performance loss during exercise in simulated Tokyo environmental conditions among elite athletes.105 Elite outdoor athletes (endurance, skill, power and mixed trained) participated in this crossover study. Participants performed a standardized exercise test in control (15.8 ± 1.2 °C, 55 ± 6% relative humidity (RH)) and simulated Tokyo (31.6 ± 1.0 °C, 74 ± 5% RH) conditions to determine performance loss. TS was assessed ± 5 min prior to exercise (iTS) and every 5 min during the incremental exercise test (TS). Based on iTS in the Tokyo condition, participants were allocated to a neutral (iTS = 0, n = 11), slightly warm (iTS = 1, n = 50), or warm-to-hot (iTS = 2/3, n = 44) subgroup.For the whole cohort iTS was 1 [1-2] and TS increased to 3 [3-3] at the end of exercise in the Tokyo condition. Average performance loss was 26.0 ± 10.7% in the Tokyo versus control condition. The slightly warm subgroup had less performance loss (22.3 ± 11.3%) compared to the warm-to-hot subgroup (29.4 ± 8.5%, p = 0.003), whereas the neutral subgroup did not respond different (28.8 ± 11.0%, p = 0.18) from the slightly warm subgroup.iTS impacted the magnitude of performance loss among elite athletes exercising in hot and humid conditions. Athletes with a warm-to-hot iTS had more performance loss compared to counterparts with a slightly warm iTS, indicating that pre-cooling strategies and/or heat acclimation may be of additional importance for athletes in the warm-to-hot iTS group to mitigate the impact of heat stress.

Native Americans (NAs) have a higher prevalence of chronic pain than other U.S. racial/ethnic groups, but there have been few attempts to understand the mechanisms of this pain disparity. This study used a comprehensive battery of laboratory tasks to assess peripheral fiber function (cool/warm detection thresholds), pain sensitivity (eg, thresholds/tolerances), central sensitization (eg, temporal summation), and pain inhibition (conditioned pain modulation) in healthy, pain-free adults (N = 155 NAs, N = 150 non-Hispanic Whites [NHWs]). Multiple pain stimulus modalities were used (eg, cold, heat, pressure, ischemic, and electric), and subjective (eg, pain ratings and pain tolerance) and physiological (eg, nociceptive flexion reflex) outcomes were measured. There were no group differences on any measure, except that NAs had lower cold-pressor pain thresholds and tolerances, indicating greater pain sensitivity than NHWs. These findings suggest that there are no group differences between healthy NAs and NHWs on peripheral fiber function, central sensitization, or central pain inhibition, but NAs may have greater sensitivity to cold pain. Future studies are needed to examine potential within-group factors that might contribute to NA pain risk.

Thermo-test devices are rarely used outside specialized pain centres because of high acquisition costs. Recently, a new, portable device ("Q-Sense") was introduced, which is less expensive but has reduced cooling capacity (20°C). We assessed the reliability/validity of the "Q-Sense" by comparing it with the Thermal Sensory Analyzer (TSA).Using a phantom-skin model, the physical characteristics of both devices were compared. The clinical performance was assessed in a multicentre study by performing Quantitative Sensory Testing (QST) in 121 healthy volunteers and 83 diabetic patients (Eudra-Med-No. CIV-12-05-006501).Both device types showed ~40% slower temperature ramps for heating/cooling than nominal data. Cold/warm detection thresholds (CDT, WDT) and heat pain thresholds (HPT) of healthy subjects did not differ between device types. Cold pain thresholds (CPT) were biased for Q-Sense by a floor effect (p .001). According to intraclass correlation coefficients (ICC), agreement between TSA and Q-Sense was good/excellent for CDT (ICC = 0.894) and WDT (ICC = 0.898), moderate for HPT (ICC = 0.525) and poor for CPT (ICC = 0.305). In diabetic patients, the sensitivity of Q-Sense to detect cold hypoesthesia was reduced in males60 years. Moderate correlations between thermal detection thresholds and morphological data from skin biopsies (n = 51) were similar for both devices.Physical characteristics of both thermo-test devices are similarly limited by the poor temperature conduction of the skin. The Q-Sense is useful for thermal detection thresholds but of limited use for pain thresholds. For full clinical use, the lower cut-off temperature should be set to ≤18°C.High purchase costs prevent a widespread use of thermo-test devices for diagnosing small fibre neuropathy. The air-cooled "Q-Sense" could be a lower cost alternative, but its technical/clinical performance needs to be assessed because of its restricted cut-off for cooling (20°C). This study provides critical information on the physical characteristics and the clinical validity/reliability of the Q-Sense compared to the "Thermal Sensory Analyzer" (TSA). We recommend lowering the cut-off value of the Q-Sense to ≤18°C for its full clinical use.

BACKGROUND Myotonic dystrophy type 1 (DM1) is a multisystem disorder affecting the peripheral nervous system. However, studies evaluating somatic small fiber sensory nerve function, which may contribute to pain in DM1, are lacking. METHODS Using quantitative sensory testing of the hand and foot, we evaluated Aδ and C-fiber function. Of 20 adult DM1 patients recruited, 16 were analyzed. Their results were compared with those of 32 age- and sex-matched controls. RESULTS No DM1 patient had diabetes mellitus or clinical evidence of small fiber neuropathy. In DM1, hand (P

Background Three TRPV1 (Transient Receptor Potential Vanilloid Receptor 1) antagonists were developed for testing in situ in human skin (Sjogren et al., 2016; Sjogren et al., 2018; Sjogren et al., 2018). The first human study using these compounds and capsaicin, was performed to determine the required local antagonist concentrations needed for target engagement (Proof of Mechanism, PoM) (Sjogren et al., 2018). In this paper, the aim was to address a TRPV1 antagonist's ability to inhibit a more complex pain signal and to define translational endpoints that could be used in further drug development, when progressing orally bioavailable TRPV1 antagonists as novel analgesic medications. Method This was a single centre, placebo-controlled, clinical proof of principle (PoP) study in 25 healthy volunteers. The subjects were exposed to UV irradiation, causing a local tissue inflammation. Three different doses of AZ12048189 were administered to assess pain perception through quantitative sensory testing (QST) and erythema using Laser Doppler scanning. Results AZ12048189 increased the warmth detection threshold (WDT) and the heat pain threshold (HPT) and decreased the intensity of supra threshold heat pain (STHP). AZ12048189 did not, however, have any significant effects as assessed using mechanical stimulation or Laser Doppler. Conclusions This study validated translational tools to confirm target engagement for TRPV1 antagonists; WDT, HPT and STHP have utility in this respect, after oral administration of a TRPV1 antagonist. This study also proved that TRPV1 antagonists can inhibit a more complex, non-capsaicin dependent thermally induced pain signal.

Human cold perception and nociception play an important role in persisting pain. However, species differences in the target temperature of thermosensitive ion channels expressed in peripheral nerve endings have fueled discussions about the mechanism of cold nociception in humans. Most frequently implicated thermosensors are members of the transient receptor potential (TRP) ion channel family TRPM8 and TRPA1. Regularly observed, distinct cold pain phenotype groups suggested the existence of interindividually differing molecular bases. In 28 subjects displaying either high or medium sensitivity to local cooling of the skin, the density at epidermal nerve fibers of TRPM8, but not that of TRPA1 expression, correlated significantly with the cold pain threshold. Moreover, reproducible grouping of the subjects, based on high or medium sensitivity to cooling, was reflected in an analogous grouping based on high or low TRPM8 expression at epidermal nerve fibers. The distribution of TRPM8 expression in epidermal nerve fibers provided an explanation for the previously observed (bi)modal distribution of human cold pain thresholds which was reproduced in this study. In the light of current controversies on the role of human TRPA1 ion channels in cold pain perception, the present observations demonstrating a lack of association of TRPA1 channel expression with cold sensitivity-related measures reinforce doubts about involvement of this channel in cold pain in humans. Since TRP inhibitors targeting TRPM8 and TRPA1 are currently entering clinical phases of drug development, the existence of known species differences, in particular in the function of TRPA1, emphasizes the increasing importance of new methods to directly approach the roles of TRPs in humans.

Ajjimaporn, A, Chaunchaiyakul, R, Pitsamai, S, and Widjaja, W. Effect of cold shower on recovery from high-intensity cycling in the heat. J Strength Cond Res 33(8): 2233-2240, 2019-Post-exercise cooling, e.g., cold water immersion has shown beneficial cardiovascular and hormonal effects during recovery from exercise in a hot environment. However, not much is known about the effects of a cold water shower (CWS) as a recovery intervention. This study examined the effects of a CWS on heart rate (HR), core temperature (Tc), salivary cortisol, and thermal comfort sensation (TCS) after exercise in the heat. Nine healthy male subjects (age, 21 ± 1 year) performed 45 minutes of cycling in a hot environment (35° C, 40-60% relative humidity) at 65% of peak oxygen uptake. Thereafter, subjects underwent the CWS condition (15 minutes, 15° C water shower) or control (SIT25; 15 minutes passive recovery in 25° C room) in a randomized crossover design. After each 15 minutes, subjects sat in a 25° C room for another 2-hour recovery. Heart rate, Tc, and TCS were recorded before and immediately after exercise, immediately after CWS or SIT25, and at 30 minutes, 1, and 2 hours during additional recovery. Salivary cortisol was collected at the same time points except at 30 minutes of the additional recovery period. Thermal comfort sensation was higher immediately after CWS (+4; very comfortable) than SIT25 (+1; just comfortable). The change of HR decreased faster with CWS (-18.3 ± 2.3%) than with SIT25 (-7.0 ± 4.6%) at the first 30-minute recovery time point (p < 0.01). No differences between recovery conditions were observed for the Tc or salivary cortisol at any time point during the 2-hour recovery period. The findings demonstrate that a 15-minute, 15° C CWS was not effective in reducing Tc or salivary cortisol during recovery from exercise in a hot environment. However, CWS can promote TCS by facilitating a faster HR recovery after 30-minute postintervention compared with passive recovery. The cooling benefits of a CWS could be only recommended to reduce cardiac stress after routine workout in a hot environment.

AIMS: To compare somatosensory function profiles and psychologic factors in patients with primary burning mouth syndrome (BMS) and healthy controls and to evaluate correlations of subjective pain ratings with somatosensory and psychologic parameters.METHODS: A quantitative sensory testing (QST) protocol-including cold detection threshold (CDT), warmth detection threshold (WDT), thermal sensory limen (TSL), paradoxical heat sensation (PHS), cold pain threshold (CPT), heat pain threshold (HPT), mechanical pain threshold (MPT), wind-up ratio (WUR), and pressure pain threshold (PPT)-was performed at the oral mucosa of the tongue, buccal, and palatal sites in 30 Chinese patients (25 women and 5 men, mean age 50.9 ± 9.2 years) with primary BMS and in 18 age- and gender-matched healthy controls (15 women and 3 men, mean age 53.2 ± 7.0 years). For each BMS patient, z scores and loss/gain scores were computed. Psychologic status was evaluated in both groups using the Self-Rating Anxiety Scale and Self-Rating Depression Scale. Correlations of BMS patients' subjective pain ratings with somatosensory and psychologic profiles were assessed with the use of Pearson or Spearman correlations and multiple linear regression.RESULTS: In BMS patients, 53.3% had somatosensory abnormalities according to z scores vs 22.2% of healthy controls (P = .033). The abnormalities in BMS patients were somatosensory loss to thermal nonnoxious stimuli (TSL = 20.0%, CDT = 13.3%, WDT = 13.3%), mechanical pressure stimuli (PPT = 16.7%), pinprick stimuli (MPT = 6.7%), and thermal pain stimuli (CPT = 3.3%), and somatosensory gain to repetitive pinprick stimuli (WUR = 6.7%), pressure stimuli (PPT = 6.7%), and thermal pain stimuli (HPT = 3.3%). The most frequent loss/gain score was 13.3% for loss of thermal somatosensory function with no somatosensory gain; 13.3% for loss of thermal and mechanical somatosensory function with no somatosensory gain; and 13.3% for gain of mechanical somatosensory function with no somatosensory loss. Mild elevations in anxiety scores were seen in 30% of the BMS patients, and 50% and 36.7% had mild and moderate elevations, respectively, in depression scores. No anxiety or depression was detected in the control group. QST results, but not psychologic scores, were significantly correlated with patients' subjective pain ratings (PHS, Spearman coefficient -0.384, P = .029; CPT, Pearson coefficient -0.370, P = .034; MPT, Pearson coefficient -0.376, P = .032; PPT, Pearson coefficient 0.363, P = .037).CONCLUSION: The present findings documented distinct differences in somatosensory function in patients with primary BMS compared to controls, indicating a complex pathophysiology and interaction between impairments in nociceptive processing and psychologic functioning.

Context Exertional heatstroke is one of the leading causes of death in American football players. Precooling (PC) with whole-body cold-water immersion (CWI) may prevent severe hyperthermia and, possibly, exertional heatstroke. However, it is unknown how much PC delays severe hyperthermia when participants wear American football uniforms during exercise in the heat. Does PC alter the effectiveness of CWI once participants become hyperthermic or affect perceptual variables during exercise? Objectives We asked 3 questions: (1) Does PC affect how quickly participants become hyperthermic during exercise in the heat? (2) Does PC before exercise affect rectal temperature (Trec) cooling rates once participants become hyperthermic? (3) Does PC affect perceptual variables such as rating of perceived exertion (RPE), thermal sensation, and environmental symptoms questionnaire (ESQ) responses? Design Crossover study. Setting Laboratory. Patients or Other Participants Twelve physically active males (age = 24 ± 4 years, height = 181.8 ± 8.4 cm, mass = 79.9 ± 10.3 kg). Intervention(s) On PC days, participants completed 15 minutes of CWI (9.98°C ± 0.04°C). They donned American football uniforms and exercised in the heat (temperature = 39.1°C ± 0.3°C, relative humidity = 36% ± 2%) until Trec was 39.5°C. While wearing equipment, they then underwent CWI until Trec was 38°C. Control-day procedures were the same except for the PC intervention. Main Outcome Measure(s) Rectal temperature, heart rate, thermal sensation, RPE, and ESQ responses were measured throughout testing. The duration of cold-water immersion was used in conjunction with Trec to calculate cooling rates. Results Precooling allowed participants to exercise 17.6 ± 3.6 minutes longer before reaching 39.5°C (t11 = 17.0, P < .001). Precooling did not affect postexercise CWI Trec cooling rates (PC = 0.18°C/min ± 0.06°C/min, control = 0.20°C/min ± 0.09°C/min; t11 = 0.9, P = .17); ESQ responses (F2,24 = 1.3, P = .3); or RPE (F2,22 = 2.9, P = .07). Precooling temporarily lowered thermal sensation (F3,26 = 21.7, P < .001) and heart rate (F3,29 = 21.0, P < .001) during exercise. Conclusions Because PC delayed hyperthermia without negatively affecting perceptual variables or CWI effectiveness, clinicians may consider implementing PC along with other proven strategies for preventing heat illness (eg, acclimatization).

Background Temporal changes of pain perception to prolonged tonic heat pain are conventionally assessed using a computerized visual analog scale. Such a rating-based approach is, however, prone to floor and ceiling effects, which limit the assessment of temporal changes in perception. Thus, alternative methods that overcome these shortcomings are warranted. New method The aim of this study was to assess the feasibility and reliability of a psychophysical approach, i.e., participant-controlled temperature (PCT), to evaluate ongoing human perception of tonic heat pain. Fifty participants were presented with a 45 °C stimulus on the non-dominant hand, and were instructed to maintain their initial sensation for two minutes via a feedback controller in the dominant hand. A subset of participants (n = 17) performed PCT tonic heat protocols on two different days to determine the test-retest reliability. As participants controlled temperature to maintain a stable pain perception, any adjustments made reflected shifts in their perception of heat. Results In 33 (71.7%) participants, we observed an initial adaptation (participant increased temperature) followed by temporal summation of pain (participant decreased temperature). Twelve participants (26.1%) showed only adaptation and one (2.2%) only temporal summation. No sex differences were observed, nor did the initial rating of pain have an effect on PCT outcomes. Temporal summation of pain showed moderate to substantial reliability upon retest. Conclusions PCT represents can be reliably performed using a contact heat stimulator to measure the temporal summation of pain. The standardized setup and overall good reliability of the outcome measures facilitate a sound implementation into the clinical work-up of patients with pain conditions.

Hypothermia can occur during aquatic exercise despite production of significant amounts of heat by the active muscles. Because the characteristics of human thermoregulatory responses to cold during exercise have not been fully elucidated, we investigated the effect of low-intensity exercise on the shivering response to core cooling in cool water. Eight healthy young men (24 ± 3 yr) were cooled through cool water immersion while resting (rest trial) and during loadless pedaling on a water cycle ergometer (exercise trial). Before the cooling, body temperature was elevated by hot water immersion to clearly detect a core temperature at which shivering initiates. Throughout the cooling period, mean skin temperature remained around the water temperature (25°C) in both trials, whereas esophageal temperature (Tes) did not differ between the trials ( P > 0.05). The Tes at which oxygen uptake (V̇o2) rapidly increased, an index of the core temperature threshold for shivering, was lower during exercise than rest (36.2 ± 0.4°C vs. 36.5 ± 0.4°C, P < 0.05). The sensitivity of the shivering response, as indicated by the slope of the Tes-V̇o2 relation, did not differ between the trials (−441.3 ±177.4 ml·min−1·°C−1 vs. −411.8 ± 268.1 ml·min−1·°C−1, P > 0.05). The thermal sensation response to core cooling, assessed from the slope and intercept of the regression line relating Tes and thermal sensation, did not differ between the trials ( P > 0.05). These results suggest that the core temperature threshold for shivering is delayed during low-intensity exercise in cool water compared with rest although shivering sensitivity is unaffected.

ObjectivesTo provide a rationale for minimum water temperature rules for elite and subelite marathon swim racing and highlight factors that make individuals vulnerable to excessive cooling during open water swimming.Methods12 lean competitive swimmers swam for up to 2 hours, three times in different water temperatures between 14°C and 20°C, wearing standard swimming costumes and hats. Rectal temperature (Tre), oxygen consumption, perception of cold and performance were measured.ResultsIn 16°C, half the swimmers did not complete a 2-hour swim; four became (or were predicted to become) hypothermic within 2 hours. In 18°C, three-quarters completed the swim; three became (or were predicted to become) hypothermic. In 20°C, one swimmer was predicted to become hypothermic in under 2 hours. The mean linear rate of fall of Trewas greater in 16°C (−1.57°C/hour) than 18°C (−1.07°C/hour) (p=0.03). There was no change in swimming performance during the swims or between conditions. Most of the cooling rate could be explained by metabolic heat production and morphology for both 16°C (R2=0.94, p2=0.82, preand perception of thermal sensation (r=0.25, p=0.13), and there was a weak correlation between Treand thermal comfort (r=0.32, p=0.04).ConclusionWe recommend that 16°C and 18°C water are too cold for elite marathon swim racing. FédérationInternationale de Natation rules were changed in 2017 to make wetsuits compulsory below 18°C and optional below 20°C.

Optimism is associated with lower pain sensitivity, positive adjustment to chronic pain, and greater reduction of pain thresholds in a conditioned pain modulation (CPM) paradigm. We hypothesized that participants with higher levels of optimism would experience greater inhibition of suprathreshold pain during CPM. Seventy-seven healthy adults completed a test of optimism, the Life Orientation Test-Revised, as well as measures of depression, pain catastrophizing, and neuroticism. Participants also underwent psychophysical tests of heat pain tolerance, heat pain threshold, and CPM. CPM magnitude was calculated as the change in heat pain ratings when applied alone and simultaneously with painful pressure. Greater optimism was significantly correlated with reduced CPM magnitude (P = .013). Regression analysis was performed using optimism as a predictor of CPM magnitude while controlling for pain catastrophizing, neuroticism, depression, and age. The overall model was significant (P = .003). Significant positive coefficients were found for depression (P = .014) and optimism (P.001) scores. These results suggest that greater optimism predicts less inhibition of suprathreshold pain, the opposite of our hypothesis. This unexpected finding may be due to factors such as perceived stress and coping differences, and suggests that modulation of threshold-level and suprathreshold pain involves different underlying mechanisms. PERSPECTIVE: This article reports that greater optimism predicts less inhibition of suprathreshold pain, in contrast with previous work showing that optimism correlates positively with pain threshold reductions. These findings suggest that the association between optimism and the function of endogenous pain modulatory systems is complex and differs for threshold-level and suprathreshold pain.

Background: Although acute thermal stress appears to be one of the most effective stressors that increase the intra- and extracellular concentrations of heat shock protein 72 (Hsp72), 17β-estradiol has been shown to inhibit heat-induced Hsp72 expression. Materials and Methods: To determine whether severe whole-body hyperthermia (increase in rectal temperature up to 39.5 °C) induced by lower-body heating is a sufficient stimulus to modulate hormonal (17β-estradiol, progesterone, prolactin, epinephrine, and norepinephrine) and extracellular Hsp72 responses, we investigated young adult women (21 ± 1 yr). Results and Conclusions: In the present study, we show that a severe whole-body hyperthermia (increase in rectal temperature of approximately 2.6 °C and heart rate of approximately 80 bpm from baseline) was sufficient to increase 17β-estradiol, progesterone, and prolactin and catecholamine norepinephrine concentration. Moreover, we show that the concentration of extracellular Hsp72 and catecholamine epinephrine were not affected by severe whole-body hyperthermia in young adult women. From the functional point of view, expression of ovarian hormones induced by passive heat stress may have therapeutic potential for young adult women in, for example, estrogen treatment and overall women’s health.

Background: Increased facial warmth sensations could lead to thermal discomfort, and different facial regions may demonstrate concurrent temperature differences. The study aim was examining facial warmth sensitivity differences by facial region under differing environmental conditions. Methods: Twelve men had heat flux measurements of six facial regions during 30 min each of rest in thermoneutral conditions (25 °C, 30% relative humidity (RH)), rest in warm conditions (40 °C, 30% RH), and cycling at 400 W of metabolic heat production (40 °C, 30% RH). Results: The forehead demonstrated highest temperatures at termination of all study conditions; lowest temperatures were noted for the nose under thermoneutral conditions and chin during warmth and exercise conditions. Five of six facial regions demonstrated significant differences in warmth sensitivity, decreasing to two of six regions during warm conditions and one of six regions during exercise, with the upper lip most sensitive in all conditions. Body thermal comfort (TC) perceptions, regressed individually on mean facial temperature (Tface) vs. core temperature (Tco), indicated that Tface was significantly more related than Tco to perceived TC (p = .001). Perceived TC, regressed individually on perceived overall body thermal sensation (TS) vs. facial TS, demonstrated that Tface was significantly more related to perceived TC (p = .004). Conclusion: There were regional differences in facial warmth sensitivity together with different facial temperatures moving toward equilibration when the body is subjected to heat-producing activities. Perceptions of TC were more strongly related to Tface than to Tco or overall body TS.

Some studies revealed that steady-uniform thermal environments are not the optimal environmental state to ensure thermal comfort, and temperature ramps offer potential advantages over traditional air conditioning methods. Moreover, when exposed to the same environmental conditions, gender differences in thermal responses were often observed, but the gender differences in the ramped conditions and causal relationships remain unclear. Therefore, an experimental research was conducted in a chamber by controlling the rates and directions to study the gender differences in thermal responses to temperature ramps. Three temperature ramps conditions (A: 26 °C-24 °C-26 °C; B: 26 °C-28 °C-26 °C; C: 26 °C-30 °C-26 °C) were investigated with 60 healthy participants (30 females and 30 males) recruited. The main conclusions indicated that women are more sensitive to temperature ramp-down environments than those of their male counterparts. Direction of temperature ramps had a significant effect on human responses in cool environments but no effect was observed in warm environments. Moreover, there was no significant differences in subjective responses between genders in a 2 °C ramp-up environment from 26 °C to 28 °C. Due to psychological differences, men have a wider range of temperature acceptability than women. Furthermore, the relationships between thermal sensation and thermal comfort, thermal sensation and thermal acceptability were also established, indicating that thermal sensation had significant impacts on other psychological responses. This paper has reference value for related researchers and designers to take temperature ramps and gender differences account in the design of indoor thermal environments, which benefits to improve thermal comfort, health and energy efficiency.

This study investigated the influence of whole body cooling on local thermal sensitivity to warm (40°C) and cold (20°C) stimuli in 10 young (age: 24 ± 2 yrs) and 10 older males (age: 69 ± 4 yrs).Local warm and cold sensitivity was assessed at eight body regions using a 25 cmWhole body cooling blunted local cold sensitivity but warm sensitivity was maintained in both age groups. Furthermore, a significant age-related decline (from young to older group) in sensitivity to a warm stimulus was observed in both NEUT and COLD conditions. Older males also had a greater ΔTThe observed interaction effect of local cold stimulation and whole body cooling may be related to both stimuli triggering similar TRP channels, whereas the lack of interaction between local warm stimuli and whole body cooling may be related to these two stimuli triggering different TRP channels. The findings reiterate the potential thermoregulatory risks (e.g. cold injury and hypothermia) associated with ageing, even with such short exposure times.

Humans often experience wet stimuli using their hands, yet we know little on how sensitive our fingers are to wetness and the mechanisms underlying this sensory function. We therefore aimed to quantify the minimum amount of water required to detect wetness on the human index fingerpad, the wetness detection threshold, and assess its modulation by temperature. Eight blinded participants (24.0 ± 5.2 y; 23.3 ± 3.5 BMI) used their index fingerpad to statically touch stimuli varying in volume (0, 10, 20, 30, 40 or 50 ml) and temperature (25, 29, 33 or 37 °C). During and post contact, participants rated wetness and thermal sensations using a modified yes/no task and a visual analogue scale. The wetness detection threshold at a moisture temperature akin to human skin (33 °C) was 24.7 ± 3.2ml. This threshold shifted depending on moisture temperature (P = 0.002), with cooler temperatures reducing (18.7 ± 3.9ml at 29 °C) and warmer temperatures increasing (27.0 ± 3.0ml at 37 °C) thresholds. When normalised over contact area, the wetness detection threshold at 33 °C corresponded to 1.926x10-4 ml mm-2 (95% CI: 1.873x10-4, 1.979x10-4 ml mm-2). Threshold differences were reflected by magnitude estimation data, which were analysed using linear regression to show that both volume and moisture temperature can predict magnitude estimations of wetness (P < 0.001). Our results indicate high sensitivity to wetness in the human index fingerpad, which can be modulated by moisture temperature. These findings are relevant for the design of products with wetness management properties.

Pain sensitivity differs individually, but the mechanisms and genetic factors that underlie these differences are not fully understood. To investigate genetic factors that are involved in sensing cold pain, we applied a cold-induced pain test and evaluated protease-activated receptor 2 (PAR2/F2RL1) and transient receptor potential melastatin 8 (TRPM8), which are related to pain. We statistically investigated the associations between genetic polymorphisms and cold pain sensitivity in 461 healthy patients who were scheduled to undergo cosmetic orthognathic surgery for mandibular prognathism. We found an association between cold pain sensitivity and the rs2243057 polymorphism of the

In warm conditions topical application of menthol increases cool sensations and influences deep body temperature. The purpose of this experiment was to explore whether different body surface areas (BSA) exposed to menthol influence these responses. It was hypothesized that the forcing function exerted by menthol will be proportionally related to BSA.Using a within-participant design, 13 participants underwent three BSA exposures (Small [S; finger]; Medium [M; arm]; Large [L; upper/lower body]) to 4.13% menthol, and one Placebo exposure. During each exposure participants rested supine in a tent (30 °C, 50%rh) for 30-min before their intervention and 30-min thereafter. Measures included thermal sensation, thermal comfort, irritation, skin blood flow (finger SkBF; laser Doppler flowmetry), rectal temperature (Tre), and skin temperature (chest, forearm, thigh, calf). The Area Under the Curve from minute 30 to 60 was calculated and analyzed using a one-way ANOVA or Friedman's test with post-hoc testing (0.05 alpha level).There was no significant difference in any measure of thermometry (p 0.05), while SKBF was significantly lowered in L, M, and S vs. P respectively (p 0.05). Participants in L felt cooler vs. P and S (p 0.05). Losses in thermal comfort were noted in L and M vs. P and S (p 0.05), along with increased irritation in L vs. S (p 0.05).Despite similar skin temperatures, larger BSA's exposed to menthol caused cooler sensations, likely due to the activation of a larger pool of menthol-sensitive neurons. This occurred in the absence of thermal discomfort and without perceptions of irritation exceeding 'weak'. Larger BSA's also exhibited greater alterations in Tre, likely driven by a reduction in SkBF, but despite this mean body temperature was regulated suggesting the thermoregulatory system can cope with the range of BSA exposures studied herein.

Heat acclimation (HA) is a widely recognized physiological phenomenon of human body in hot environments. HA has many benefits, such aspreventing hyperthermia responses, and is an efficient way to improve human responses to hyperthermal environments. However, it is not known whether HA is dependent on the environmental conditions. Moreover, its mechanism and effect on the safety performance remain unexplored. In this study, we created a climate chamber to simulate a hyperthermal environment. Thirty healthy males were recruited for this study, who were then trained under the same ambient conditions (temperature of 38 °C and relative humidity (RH) of 40%). The training involved running on treadmills (at 5 km/h) to simulate heavy manual labor, and performing heat stress tests (HST) under six different conditions (32 °C/40% RH, 35 °C/40%, 38 °C/40%, 32 °C/70%, 35 °C/70%, and 38 °C/70%). Their physiological indices (rectal temperature, heart rate, sweat loss and skin temperature) and one psychological index (thermal sensation) were measured. Furthermore, a hazard avoidance test device (HATD) was designed to evaluate the individual safety performance by detecting human errors. The results show that training and environmental conditions have different effects on HA. After HA, the physiological and psychological strain were significantly improved. More importantly, HA also helped improve the participants’ awareness of the dangers and required emergency responses to face potential hazards. Overall, a reasonable HA training under proper conditions is helpful to ensure the safety of human beings. More research is needed to study the role of HA on safety performance.

Purpose To examine the effects of prolonged intermittent exposures to moderately increased transmural pressure on finger vasoreactivity and thermoperception to localised cooling. Methods Eleven men completed a 5-week regimen (3 sessions·week−1; 55 min·session−1), during which the vasculature in one arm (EXP) was exposed intermittently (10-min exposure: 5-min pause) to increased transmural pressure (from +65 mmHg week-1 to +105 mmHg week-5). Before and after the regimen, finger cutaneous vascular conductance (CVC), temperature (Tavg), and thermoperception (thermal sensation, discomfort and pain) were monitored during a 30-min hand cold (8 °C water) provocation trial. The responses of the non-trained hand were examined during an additional cold trial. Results After the regimen, baseline finger CVC and Tavg were higher in both hands (p ≤ 0.01). During cooling, neither finger CVC nor Tavg were modified (p > 0.05). Yet the magnitude of the cold-induced drop of CVC was augmented in both hands, and to a similar extent (p ≤ 0.02). The regimen alleviated thermal pain in both hands (p ≤ 0.02); the sensation of coldness and thermal discomfort were attenuated mainly in the EXP hand (p = 0.02). Conclusions Present findings indicate that iterative local exposures to augmented intravascular pressure do not alter finger vasoreactivity to localised cooling. The pressure training, however, might impair finger basal vasomotor tone, and aggravate the magnitude of constrictor responsiveness to cooling. The pressure training also elicits thermoperceptual desensitisation to noxious thermal stimulus. To large extent, these vascular and perceptual adjustments seem to be transferred to the cutaneous vasculature of the non-trained limb.

Fish farming is considered as a physical demanding occupation, including work operations with high workloads and awkward work positions for prolonged periods of time. Combined with potential challenging environmental conditions, these factors may negatively affect work performance, comfort and health. This study aimed to explore work strain and thermophysiological responses in Norwegian fish farming. Fourteen workers (age 35 ± 15 yrs) from four fish farms participated in the field studies, and measurements of heart rate (HR), core- and skin temperatures were registered continuously during a work shift. Questions about subjective thermal sensation and comfort were answered. This study has shown that workers at fish farms are periodically exposed to high or low levels of work strain, where the high workloads are manifested as increased core temperature and HR when working. The results are expected to give a better understanding of work strain and environmental challenges during fish farm operations.

Diurnal changes in physiological and behavioral responses to constant relative humidity (RH) were investigated in summer to validate a hypothesis that thermal sensation responses (TSR) vary with the diurnal cycle while maintained at stable RH's of 60, 70, or 80%. Seven lightly clothed male subjects were exposed to one of three RH while air temperature (Ta) was held at 28 °C from 9:00–18:30. Mean skin temperature ( T ¯ sk ) and tympanic temperature (Tty) were monitored at 2-min intervals throughout the experimental period. Cutaneous warm and cool sensation thresholds and stratum corneum water content (SCWC) on the anterior forearm, posterior forearm, and anterior thigh, finger blood flow rate (SkBF) were measured by a thermal stimulator controlled by a Peltier element (Intercross-230; Intercross, Co., Tokyo, Japan), a water content of stratum corneum monitor (Corneometer CM825 & MPA 5; Integral Co., Tokyo, Japan), and a laser flowmeter (ALF21; Advance Co., Tokyo, Japan), accordingly at the end of three periods: 9:30–10:30, 13:30–14:30, and 17:30–18:30. The TSR and the thermal comfort response were also recorded using subjective scales of thermal sensation and comfort thresholds at the end of three periods. The Tty and mean skin temperature ( T ¯ sk ) remained unchanged during the day under all RH conditions. Temperature difference between warm and cold sensation thresholds and SkBF decreased slightly towards the evening under all RH conditions whereas SCWC increased from the morning to the evening at 60% and 80% RH. Behaviorally, the subjects responded more than “slightly warm” at 70%, and 80% RH, and then the TSR changed significantly (p

Objectives To investigate the effects of pre- and per-cooling interventions on subsequent 15-min time-trial (TT) cycling performance in the heat. Design Randomized cross-over design. Methods Nine male athletes completed four experimental trials in the heat (40 °C, 50% rh): no-cooling (CON); warm-up per-cooling (PER: neck-cooling collar applied during the preload); pre-cooling (PRE: 30 min of cold water (22 °C) immersion [CWI]); and pre- and per-cooling combined (PRE + PER). In each trial, participants completed a 45-min preload exercise (50% VO2peak), followed by a 15-min TT. Physiological (rectal [Tre], skin [Tsk], and neck [Tneck] temperature, and heart rate [HR]) and perceptual data (ratings of perceived exertion [RPE], thermal comfort [TC] and thermal sensation [TS]) were measured throughout. Results Tre and Tsk were lower in PRE and PRE + PER at the start of the preload (p Conclusions Pre-cooling induced thermoregulatory benefits for ~45 min and perceptual benefits for the same duration when supplemented with per-cooling. Neck per-cooling offered no such benefits when used in isolation. Neither pre- nor per-cooling, in isolation or combination, improved subsequent 15-min cycling time-trial performance in well-trained participants in the heat (40 °C).

In the context of a generative model, such as predictive coding, pain and heat perception can be construed as the integration of expectation and input with their difference denoted as a prediction error. In a previous neuroimaging study (Geuter et al., 2017) we observed an important role of the insula in such a model, but could not establish its temporal aspects. Here we employed electroencephalography to investigate neural representations of predictions and prediction errors in heat and pain processing. Our data show that alpha-to-beta activity was associated with stimulus intensity expectation, followed by a negative modulation of gamma band activity by absolute prediction errors. This is in contrast to prediction errors in visual and auditory perception, which are associated with increased gamma band activity, but is in agreement with observations in working memory and word matching, which show gamma band activity for correct, rather than violated predictions.

BACKGROUND: \ud Cycling downhill accelerates heat loss and requires lower work rates leading to cold discomfort. Historically, cyclists have behaviorally thermoregulated prior to cycling downhill by inserting newspapers into their jerseys. Yet, there is no experimental data to support such a method showing improvements in thermal perception and profile; we hypothesized it would. \ud METHODS: \ud Two cohorts (n=8 each) of male participants completed two main trials each involving 30-minutes simulated uphill cycling (65% VO2peak 188 (41)W; no fan) followed by 15-minutes downhill cycling (35% VO2peak 41 (12)W) in front of an industrial fan (wind speed: 4.6 (0.1)m·s-1). In one trial participants inserted one (study 1) or two (study 2) tabloid newspapers into their jerseys (PAPER) prior to downhill cycling; the other was a control (NOPAPER). Whole body and torso thermal sensation (TS) and comfort (TC), aural temperature (Tau), skin temperature (Tskin), and newspaper mass change (Δ) were measured. Data were compared using ANOVA and t-test to 0.05 alpha level. RESULTS: \ud After uphill cycling thermal and perceptual profiles were similar. In study 1, only TC was transiently improved 1-minute after newspaper insertion. In study 2, Tskin rate of decline was lower in the PAPER condition (−0.11 (0.12)ºC.min-1 cf −0.53 (0.16)ºC.min-1; p = .001) and Tchest remained higher (28.83 (3.17)ºC cf 24.39 (3.22)ºC). This improved TS but not TC. Newspaper mass increased indicating impaired sweat evaporation (Δmass: 5.7 (4.9)g; p=0.01). \ud CONCLUSIONS: \ud Thermal perception and profile during downhill cycling was improved by inserting two newspapers but not one newspaper into the jersey, supporting our hypothesis.

This study assessed the influence of High (H, 4.13%), Medium (M, 2.0%) and Low (L, 0.1%) doses of menthol on temperature perception and regulation, compared to a Placebo Condition (P).Sixteen participants underwent the aforementioned conditions on four separate days. During each test participants rested supine (Environmental conditions: 30 °C, 50% rh) for 30-min before 40 mL of L, M, H or P gel was applied to the anterior upper body, then rested 30-min thereafter. Primary measures included thermal sensation (TS), thermal comfort (TC), irritation (IRR), rectal temperature (Tre), and skin temperature (chest, forearm, thigh, calf), and EMG (trapezius, pectoralis major, sternocleidomastoid). The area under the curve (AUC) from minute 30 to 60 was compared between conditions using relevant non/parametric tests (alpha level = 0.05).A cooling trend in Tre was observed following Placebo gel application, but this significantly (p 0.05) reversed into a heat storage response in M and H. Both TS and TC significantly differed by condition (p 0.001) in a dose-dependent manner, with L, M, and H doses eliciting significantly cooler sensations and more discomfort than P (p 0.05). Irritation significantly differed by condition (p 0.01) in a dose-dependent manner, with L and M eliciting significantly greater irritation than P (p 0.01). No other differences were observed.Menthol exerts perceptual and thermoregulatory effects independent of skin temperature. A menthol dose-dependent perceptual cooling effect was evident with possible saturation at the moderate dose. A dose-dependent alteration in deep body temperature was also evident.

To determine the vastus lateralis muscle temperature kinetics during and after passive heating, to exam the effect of sex on thermoregulatory responses, and the thermal safety and tolerance of the 42 °C hot-water immersion protocol.Thirty participants (15 males, 15 females) underwent a 2 h 42 ºC hot-water immersion to the waist level. Vastus lateralis, rectal and skin temperature, thermal sensation, heart rate and blood pressure (BP) were measured during the passive heating and recovery period. Participant recovery was monitored until muscle temperature returned to baseline.Vastus lateralis temperature increased to a maximal value of 39.0 ± 0.11 °C (P 0.001), reaching a plateau after ~ 83.5 min of hot-water immersion and returning to baseline after ~ 115.8 min of recovery. Despite the anthropometric differences between males and females (e.g., height, body mass, body fat %, and fat thickness; P 0.05), thermoregulatory responses showed no differences between sexes (P 0.05). No change was found in systolic BP (~ 117 mmHg; P = 0.061). Peak rectal temperature (38.8 ± 0.14 °C; P 0.001), heart rate (~ 100 bpm; P 0.001), and diastolic BP (↓ ~ 13 mmHg; P 0.001) during the hot-water immersion indicated the safety of the protocol. While skin temperature (~ 35.4 °C; P 0.001) and thermal sensation (~ 5.95 AU; P 0.001) confirmed protocol tolerance.These data demonstrate lower-body 42 °C hot-water immersion to increase vastus lateralis temperature and plateau ~ 2.8 °C above baseline. This amplitude of muscle temperature change aligns with reported cellular adaptation and muscle growth. Thermal strain incurred from this protocol appears safe and tolerable, positioning it well for health-related prescription.

Introduction: Chemotherapy-induced peripheral neuropathy (CIPN) is a worldwide concern in patients receiving neurotoxic agents for cancer therapy. High tone external muscle stimulation is a promising therapeutic approach to alleviate symptoms of CIPN. Methods: This pilot study aims to investigate whether the application of home-based high-tone external muscle stimulation therapy (HTEMS) improves symptoms of CIPN. The trial is planned as a therapist- and assessor-blinded, 1:1 randomized controlled study. A total of 50 patients with chemotherapy-induced peripheral polyneuropathy will be included. All patients will perform therapy at home. Study participants will be allocated randomly to the HTEMS therapy (intervention group) or to the transcutaneous electrical nerve stimulation (TENS, control group), respectively, following a standardized therapy schedule. Compliance of participants can be verified by reading out the tool box. Outcomes will be evaluated at baseline and after 8 weeks of home-based therapy. The primary outcome includes improvement of CIPN according to the patient-reported EORTC QLQ-CIPN 20 questionnaire. Secondary outcomes are the patient-reported change in health-related quality of life and clinician-reported changes of vibration sensibility, tendon reflexes, temperature sensibility, perception of touch, and strength of the lower leg muscles. Further a safety- and process evaluation will be performed. Discussion: This pilot RCT aims to evaluate the impact of home-based HTEMS as compared to TENS in CIPN. There is a need for an effective treatment for CIPN and the results of this study are expected to possibly identify a novel and effective treatment strategy in the future.

BackgroundThe Wet-Bulb Globe Temperature (WBGT) index is a common tool to screen for heat stress for sporting events. However, the index has a number of limitations. Rational indices, such as the physiological equivalent temperature (PET) and Universal Thermal Climate Index (UTCI), are potential alternatives.AimTo identify the thermal index that best predicts ambulance-required assistances and collapses during a city half marathon.MethodsEight years (2010–2017) of meteorological and ambulance transport data, including medical records, from Gothenburg’s half-marathon were used to analyse associations between WBGT, PET and UTCI and the rates of ambulance-required assistances and collapses. All associations were evaluated by Monte-Carlo simulations and leave-one-out-cross-validation.ResultsThe PET index showed the strongest correlation with both the rate of ambulance-required assistances (R2=0.72, p=0.008) and collapses (R2=0.71, p=0.008), followed by the UTCI (R2=0.64, p=0.017; R2=0.64, p=0.017) whereas the WBGT index showed substantially poorer correlations (R2=0.56, p=0.031; R2=0.56, p=0.033). PET stages of stress, match the rates of collapses better that the WBGT flag colour warning. Compared with the PET, the WBGT underestimates heat stress, especially at high radiant heat load. The rate of collapses increases with increasing heat stress; large increase from the day before the race seems to have an impact of the rate of collapses.ConclusionWe contend that the PET is a better predictor of collapses during a half marathon than the WBGT. We call for further investigation of PET as a screening tool alongside WBGT.

In homeostasis, somatosensory C fibre afferents are hypothesised to mediate input to the brain about interactions with external stimuli and sympathetic efference provides the output that regulates bodily functions. We aimed to test this hypothesis and whether different types of innocuous somatosensory input have differential effects. Healthy volunteers performed a muscle fatigue (hand-grip) task to exhaustion, which produces increased muscle sympathetic nerve activity (MSNA), as measured through microneurography. Participants completed the muscle fatigue task without concurrent cutaneous sensory stimulation (control) or we applied skin warming (heat pack) as a C fibre stimulation, slow brush stroking as C and Aβ fibre stimulation, or vibration as Aβ fibre stimulation, to the participant’s forearm. We also measured heart rate, the duration of the hand-grip task, and ratings of pain at the end of the task. Concurrent skin warming showed increased MSNA compared to the other conditions. Tactile stimuli (brushing, vibration) were not significantly different to the control (no intervention) condition. Warming increased the pain from the muscle contraction, whereas the tactile stimuli did not. We interpret the effect of warming on MSNA as providing relevant afferent information during muscle contraction, which needed to be counteracted via vasoconstriction to maintain homeostasis. Brushing and vibration were less homeostatically relevant stimuli for the muscle contraction and hence had no significant effect. The findings add sensory specificity to our current understanding of homeostatic regulation through somatosensory afferent and sympathetic efferent pathways.

This study investigated whether adjusting clothing to remain in neutral thermal comfort at moderately elevated temperature is capable of avoiding negative effects on perceived acute subclinical health symptoms, comfort, and cognitive performance. Two temperatures were examined: 23ºC and 27ºC. Twelve subjects were able to remain thermally comfortable at both temperatures by adjusting their clothing. They rated the physical environment, their comfort, the intensity of acute subclinical health symptoms, and their mental load, and they performed a number of cognitive tasks. Their physiological reactions were monitored. Their performance of several tasks was significantly worse at 27ºC, and they reported increased mental load at this temperature. Skin temperature and humidity and respiration rate were higher, while blood oxygen saturation (SpO2) and pNN50 were lower at this temperature, the latter indicating increased stress. It is inferred that the observed physiological responses were mainly responsible for the negative effects on performance, as the subjects did not indicate any increased intensity of acute subclinical health symptoms although perceived air quality was worse at the higher temperature. The present results suggest that moderately elevated temperatures should be avoided even if thermal comfort can be achieved, as it may lead to reduced performance.