Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia?

Humans are the primary sources of CO2 and NH3 indoors. Their emission rates may be influenced by human physiological and psychological status. This study investigated the impact of physiological and psychological engagements on the human emissions of CO2 and NH3. In a climate chamber, we measured CO2 and NH3 emissions from participants performing physical activities (walking and running at metabolic rates of 2.5 and 5 met, respectively) and psychological stimuli (meditation and cognitive tasks). Participants' physiological responses were recorded, including the skin temperature, electrodermal activity (EDA), and heart rate, and then analyzed for their relationship with CO2 and NH3 emissions. The results showed that physiological engagement considerably elevated per-person CO2 emission rates from 19.6 (seated) to 46.9 (2.5 met) and 115.4 L/h (5 met) and NH3 emission rates from 2.7 to 5.1 and 8.3 mg/h, respectively. CO2 emissions reduced when participants stopped running, whereas NH3 emissions continued to increase owing to their distinct emission mechanisms. Psychological engagement did not significantly alter participants' emissions of CO2 and NH3. Regression analysis revealed that CO2 emissions were predominantly correlated with heart rate, whereas NH3 emissions were mainly associated with skin temperature and EDA. These findings contribute to a deeper understanding of human metabolic emissions of CO2 and NH3.

Circadian rhythmicity in schizophrenia male patients with and without substance use disorder comorbidity.

Circadian rhythmicity is associated to clinical variables that play an important role in both schizophrenia (SZ) and substance use disorders (SUD), although the characteristics of the coexistence of these two diagnoses (SZ +) remain mostly unknown. Hence, we studied a sample of 165 male patients divided in three groups each of 55, according to their diagnoses (SZ + , SZ, and SUD), as well as a healthy control (HC; n = 90) group. Alongside with sociodemographic and clinical variables, circadian rhythms were registered through a sleep-wake data structured interview, a circadian typology questionnaire, and distal skin temperature (DST) using the Thermochron iButton every 2 min during 48 h. Analyses showed that SZ + and SZ patients presented a longer sleep (delay in wake-up time) and mostly an intermediate circadian typology, while SUD patients slept less hours, displaying a morning typology. The DST showed the highest daily activation and stability for the SUD group, even when compared with the HC group. The presence of schizophrenia (SZ + and SZ) was related to a DST pattern with a reduced amplitude determined by a wakefulness impairment, which was more pronounced for SZ patients whose sleep period was adequate. The assessment of circadian rhythms in under treatment male patients with SZ should be focused on the diurnal period as a possible marker of either treatment adherence or patient's recovery, irrespective of the presence of a comorbid SUD. Further research with additional objective measures may provide knowledge transferable to therapeutic strategies and could be useful to establish possible endophenotypes in the future.

Effect of sportswear on performance and physiological heat strain during prolonged running in moderately hot conditions.

INTRODUCTION: This study examined the impact of different upper-torso sportswear technologies on the performance and physiological heat strain of well-trained and national-level athletes during prolonged running in moderately hot conditions. METHODS: A randomized crossover design was employed in which 20 well-trained (n = 16) and national-level (n = 4) athletes completed four experimental trials in moderately hot conditions (35°C, 30% relative humidity). In each trial, participants ran at 70% of their peak oxygen uptake (70% V̇O2peak ) for 60 min, while wearing a different upper-body garment: cotton t-shirt, t-shirt with sweat-wicking fabric, compression t-shirt, and t-shirt with aluminum dots lining the inside of the upper back of the garment. Running speed was adjusted to elicit the predetermined oxygen consumption associated with 70% V̇O2peak . Physiological (core and skin temperatures, total body water loss, and urine specific gravity) and perceptual (thermal comfort and sensation, ratings of perceived exertion, and garment cooling functionality) parameters along with running speed at 70% V̇O2peak were continuously recorded. RESULTS: No significant differences were observed between the four garments for running speed at 70% V̇O2peak , physiological heat strain, and perceptual responses (all p > 0.05). The tested athletes reported larger areas of perceived suboptimal cooling functionality in the cotton t-shirt and the t-shirt with aluminum dots relative to the sweat-wicking and compression t-shirts (d: 0.43-0.52). CONCLUSION: There were not differences among the tested garments regarding running speed at 70% V̇O2peak , physiological heat strain, and perceptual responses in well-trained and national-level endurance athletes exercising in moderate heat.

Intra-day variations in volar forearm skin hydration.

BACKGROUND: Skin hydration (SKH) measurements are used for multiple purposes: to study skin physiology, to clinically investigate dermatological issues, and to assess localized skin water in pathologies like diabetes and lymphedema. Often the volar forearm is measured at various times of day (TOD). This report aims to characterize intra-day variations in volar forearm SKH to provide guidance on expected TOD dependence. MATERIALS AND METHODS: Forty medical students (20 male) self-measured tissue dielectric constant (TDC) on their non-dominant forearm in triplicate as an index of local skin tissue water every 2 h starting at 0800 and ending at 2400 h. All were trained and pre-certified in the procedure and had whole-body fat (FAT%) and water (H2O%) measured. Day average TDC (TDCAVG) was determined as the average of all time points expressed as mean ± SD. RESULTS: Males versus females had similar ages (25.1 ± 2.2 years vs. 25.1 ± 1.5 years), higher H2O% (56.6 ± 5.0 vs. 51.8 ± 5.7, p = 0.002), and higher TDCAVG (32.7 ± 4.1 vs. 28.5 ± 5.1, p = 0.008). TDC values were not significantly impacted by H2O% or FAT%. Female TDC exhibited a significant decreasing trend from morning to night (p = 0.004); male TDC showed no trend. CONCLUSION: Skin water assessed by TDC shows some intra-day variations for females and males but with quite different temporal patterns. Clinical relevance relates to the confidence level associated with skin hydration estimates when measured at different times of day during normal clinic hours which, based on the present data, is expected to be around 5% for both males and females.

Hot water immersion is associated with higher thermal comfort than dry passive heating for a similar rise in rectal temperature and plasma interleukin-6 concentration.

PURPOSE: To compare the perceptual responses and interleukin-6 (IL-6) concentration following rectal temperature-matched dry heat exposure (DH) and hot water immersion (HWI). METHODS: Twelve healthy young adults (BMI 23.5 ± 3.6 kg/m2; age: 25.8 ± 5.7 years) underwent 3 trials in randomised order: DH (air temperature 68.9 °C), HWI (water temperature 37.5 °C), and thermoneutral dry exposure (CON, air temperature 27.3 °C). Blood samples to determine IL-6 plasma concentration were collected; basic affect and thermal comfort, rectal and skin temperature (Tskin) were assessed throughout the intervention. RESULTS: Rectal temperature (Trec) did not differ between DH (end temperature 38.0 ± 0.4 °C) and HWI (37.9 ± 0.2 °C, P = 0.16), but was higher compared with CON (37.0 ± 0.3 °C; P ≤ 0.004). Plasma IL-6 concentration was similar after DH (pre to post: 0.8 ± 0.5 to 1.4 ± 1.5 pg·ml-1) and HWI (0.5 ± 0.2 to 0.9 ± 0.6 pg·ml-1; P = 0.46), but higher compared with CON (0.6 ± 0.5 to 0.6 ± 0.4 pg·ml-1; P = 0.01). At the end of the intervention, basic affect and thermal comfort were most unfavourable during DH (Basic affect; DH: - 0.7 ± 2.9, HWI: 0.8 ± 1.9, CON 1.9 ± 1.9, P ≤ 0.004; Thermal comfort; 2.6 ± 0.8, HWI: 1.4 ± 0.9 and CON: 0.2 ± 0.4; P ≤ 0.004). Mean Tskin was highest for DH, followed by HWI, and lowest for CON (DH: 38.5 ± 1.3 °C, HWI: 36.2 ± 0.5 °C, CON: 31.6 ± 0.7 °C, P < 0.001). CONCLUSION: The IL-6 response did not differ between DH and HWI when matched for the elevation in Trec. However, thermal comfort was lower during DH compared to HWI, which may be related to the higher Tskin during DH.

Cold-induced vasodilation during sequential immersions of the hand.

A common practice for those operating in cold environments includes repetitive glove doffing and donning to perform specific tasks, which creates a repetitive cycle of hand cooling and rewarming. This study aimed to determine the influence of intraday repeated hand cooling on cold-induced vasodilation (CIVD), sympathetic activation, and finger/hand temperature recovery. Eight males and two females (mean ± SD age: 28 ± 5 year; height: 181 ± 9 cm; weight: 79.9 ± 10.4 kg) performed two 30-min hand immersions in cold (4.3 ± 0.92 °C) water in an indoor environment (18 °C). Both immersions (Imm1; Imm2) were performed on the same day and both allowed for a 10-min recovery. CIVD components were calculated for each finger (index, middle, ring) during each immersion. CIVD onset time (index, p = 0.546; middle, p = 0.727; ring, p = 0.873), minimum finger temperature (index, p = 0.634; middle, p = 0.493; ring, p = 0.575), and mean finger temperature (index, p = 0.986; middle, p = 0.953; ring, p = 0.637) were all similar between immersions. Recovery rates generally demonstrated similar responses as well. Findings suggest that two sequential CIVD tests analyzing the effect of prior cold exposure of the hand does not impair the CIVD response or recovery. Such findings appear promising for those venturing into cold environments where hands are likely to be repeatedly exposed to cold temperatures.

Short-term cocoa bioflavanol supplementation does not improve cold-induced vasodilation in young healthy adults.

PURPOSE: Cold-induced vasodilation (CIVD) is an oscillatory rise in blood flow to glabrous skin that occurs in cold-exposed extremities. Dietary flavanols increase bioavailable nitric oxide, a proposed mediator of CIVD through active vasodilation and/or withdrawal of sympathetic vascular smooth muscle tone. However, no studies have examined the effects of flavanol intake on extremity skin perfusion during cold exposure. We tested the hypothesis that acute and 8-day flavanol supplementation would augment CIVD during single-digit cold water immersion (CWI). METHODS: Eleven healthy adults (24 ± 6 years; 10 M/1F) ingested cocoa flavanols (900 mg/day) or caffeine- and theobromine-matched placebo for 8 days in a double-blind, randomized, crossover design. On Days 1 and 8, CIVD was assessed 2 h post-treatment. Subjects immersed their 3rd finger in warm water (42 °C) for 15 min before CWI (4 °C) for 30 min, during which nail bed and finger pad skin temperature were measured. RESULTS: Flavanol ingestion had no effect on CIVD frequency (Day 1, Flavanol: 3 ± 2 vs. Placebo: 3 ± 2; Day 8, Flavanol: 3 ± 2 vs. Placebo: 3 ± 1) or amplitude (Day 1, Flavanol: 4.3 ± 1.7 vs. Placebo: 4.9 ± 2.6 °C; Day 8, Flavanol: 3.9 ± 1.9 vs. Placebo: 3.9 ± 2.0 °C) in the finger pad following acute or 8-day supplementation (P > 0.05). Furthermore, average, nadir, and apex finger pad temperatures during CWI were not different between treatments on Days 1 or 8 of supplementation (P > 0.05). Similarly, no differences in CIVD parameters were observed in the nail bed following supplementation (P > 0.05). CONCLUSION: These data suggest that cocoa flavanol ingestion does not alter finger CIVD. Clinical Trial Registration Clinicaltrials.gov Identifier: NCT04359082. April 24, 2020.

Skin Temperature Following Total Knee Arthroplasty: A Longitudinal Observational Study.

BACKGROUND: Total knee arthroplasty (TKA) is the most effective method of pain relief and increased functional status for end-stage knee arthritis. We aimed to assess in patients undergoing unilateral, primary TKA whether the temperature of the operated limb, compared to the nonoperative limb, remains elevated up to 1 year postoperatively. METHODS: Using a prospective, longitudinal, observational study design, 1,094 patients were enrolled, and 889 patients completed a minimum of 4 out of 5 follow-up appointments. There were 864 patients who had a normal postoperative course, while 25 patients were deemed to have a superficial or deep infection. Skin temperatures were measured using an infrared thermometer on the operated and nonoperated knees preoperatively, at 2, 6, 12 weeks, and 1 year postoperatively. A subgroup analysis was performed on the 25 patients deemed to have a superficial or deep infection. RESULTS: There was a statistically significant increase in skin temperature in the operated versus nonoperated knee at every follow-up, with a P < .001. However, the effect size was small at the 1-year follow-up, with a mean difference in skin temperature of 0.3 °C. In the infected subgroup, there was a statistically significant difference in skin temperature at 2, 6, and 12 weeks, with a greater difference in skin temperature between the operated and nonoperated knees (4.05 versus 3.78 °C in the noninfected). However, there was little clinical difference (0.27 °C) at 2 weeks between infected and noninfected patients. CONCLUSIONS: This study could improve postoperative interactions between patients and surgeons. It is normal for skin temperature post-TKA to increase initially and improve over time, but it can take up to 1 year before there is little clinical difference. Because of the small difference in the rise of skin temperature between infected and noninfected patients, there is little indication that skin temperature is a reliable indicator of infection.

Enhancing thermal comfort prediction in high-speed trains through machine learning and physiological signals integration.

Heating, Ventilation, and Air Conditioning (HVAC) systems in high-speed trains (HST) are responsible for consuming approximately 70% of non-operational energy sources, yet they frequently fail to ensure provide adequate thermal comfort for the majority of passengers. Recent advancements in portable wearable sensors have opened up new possibilities for real-time detection of occupant thermal comfort status and timely feedback to the HVAC system. However, since occupant thermal comfort is subjective and cannot be directly measured, it is generally inferred from thermal environment parameters or physiological signals of occupants within the HST compartment. This paper presents a field test conducted to assess the thermal comfort of occupants within HST compartments. Leveraging physiological signals, including skin temperature, galvanic skin reaction, heart rate, and ambient temperature, we propose a Predicted Thermal Comfort (PTC) model for HST cabin occupants and establish an intelligent regulation model for the HVAC system. Nine input factors, comprising physiological signals, individual physiological characteristics, compartment seating, and ambient temperature, were formulated for the PTS model. In order to obtain an efficient and accurate PTC prediction model for HST cabin occupants, we compared the accuracy of different subsets of features trained by Machine Learning (ML) models of Random Forest, Decision Tree, Vector Machine and K-neighbourhood. We divided all the predicted feature values into four subsets, and did hyperparameter optimisation for each ML model. The HST compartment occupant PTC prediction model trained by Random Forest model obtained 90.4% Accuracy (F1 macro = 0.889). Subsequent sensitivity analyses of the best predictive models were then performed using SHapley Additive explanation (SHAP) and data-based sensitivity analysis (DSA) methods. The development of a more accurate and operationally efficient thermal comfort prediction model for HST occupants allows for precise and detailed feedback to the HVAC system. Consequently, the HVAC system can make the most appropriate and effective air supply adjustments, leading to improved satisfaction rates for HST occupant thermal comfort and the avoidance of energy wastage caused by inaccurate and untimely predictive feedback.

Impact of Topical Capsaicin Cream on Thermoregulation and Perception While Walking in the Cold.

INTRODUCTION: Capsaicin, a chili pepper extract, can stimulate increased skin blood flow (SkBF) with a perceived warming sensation on application areas. Larger surface area application may exert a more systemic thermoregulatory response. Capsaicin could assist with maintaining heat transport to the distal extremities, minimizing cold weather injury risk. However, the thermoregulatory and perceptual impact of topical capsaicin cream application prior to exercise in the cold is unknown. METHODS: Following application of either a 0.1% capsaicin or control cream to the upper and lower extremities (10 g total, ∼40-50% body surface area), 11 participants in shorts and a t-shirt were exposed to 30 min of cold (0 °C, 40% relative humidity). Exposures comprised of 5 min seated rest, 20 min walking (1.6 m·s-1, 5% grade), and 5 min seated rest. Temperature (skin, core), SkBF, skin conductivity, heart rate, thermal sensation, and thermal comfort were measured throughout. RESULTS: The capsaicin treatment did not differ from the control treatment in skin temperature (treatment mean: 30.0 ± 2.5, 30.1 ± 2.4 °C, respectively, p = 0.655), core temperature (treatment mean: 37.3 ± 0.5, 37.4 ± 0.4 °C, respectively, p = 0.113), SkBF (treatment mean: -8.4 ± 10.0, -11.1 ± 10.7 A.U., respectively, p = 0.492), skin conductivity (treatment mean: -0.7 ± 5.1, 0.4 ± 6.4 µS, respectively, p = 0.651), or heart rate (treatment mean: 83 ± 29, 85 ± 28 beats·minute-1, respectively, p = 0.234). The capsaicin and control treatments also did not differ in thermal sensation (p = 0.521) and thermal comfort (p = 0.982), with perceptual outcomes corresponding with feeling "cool" and "just uncomfortable," respectively. CONCLUSIONS: 0.1% topical capsaicin application to exposed limbs prior to walking in a cold environment does not alter whole-body thermoregulation or thermal perception.

Evaluation of pulse oximeter at the nasal septum during general anesthesia: comparison with finger oximeter.

PURPOSE: Though the finger is generally recommended for pulse oxygen saturation (SpO2) monitoring site, its reliability may be compromised in conditions of poor peripheral perfusion. Therefore, we compared the performance of nasal septum SpO2 monitoring with finger SpO2 monitoring relative to simultaneous arterial oxygen saturation (SaO2) monitoring in generally anesthetized patients. METHODS: In 23 adult patients, comparisons of SpO2 measured at the nasal septum and finger with simultaneous SaO2 were made at four time points during the 90 min study period. A pulse oximetry monitoring failure was defined as a > 10 s continuous failure of in an adequate SpO2 data acquisition. Core temperature as well as finger-tip and nasal septum temperatures were simultaneously measured at 10 min intervals. RESULTS: A total of 92 sets of SpO2 and SaO2 measurements were obtained in 23 patients. The bias and precision for SpO2 measured at the nasal septum were - 0.8 ± 1.3 (95% confidence interval: - 1.1 to - 0.6), which was similar to those for SpO2 measured at the finger (- 0.6 ± 1.4; 95% confidence interval: - 0.9 to - 0.4) (p = 0.154). Finger-tip temperatures were consistently lower than other two temperatures at all time points (p < 0.05), reaching 33.5 ± 2.3 °C at 90 min after induction of anesthesia. While pulse oximetry monitoring failure did not occur for nasal septum probe, two cases of failure occurred for finger probe. CONCLUSIONS: Considering the higher stability to hypothermia with a similar accuracy, nasal septum pulse oximetry may be an attractive alternative to finger pulse oximetry. Trail registration This study was registered with Clinical Research Information Service (CRIS: https://cris.nih.go.kr/cris/en/ ; ref: KCT0008352).

Heel skin microclimate control: Secondary analysis of a self-controlled randomized clinical trial.

OBJECTIVE: this study was undertaken to evaluate the efficacy of multilayer polyurethane foam with silicone (MPF) compared to transparent polyurethane film (TPF) dressings in the control of heel skin microclimate (temperature and moisture) of hospitalized patients undergoing elective surgeries. METHOD: the study took of a secondary analysis of a randomized self-controlled trial, involving patients undergoing elective surgical procedure of cardiac and gastrointestinal specialties in a university hospital in southern Brazil, from March 2019 to February 2020. Patients served as their own control, with their heels randomly allocated to either TPF (control) or MPF (intervention). Skin temperature was measured using a digital infrared thermometer; and moisture determined through capacitance, at the beginning and end of surgery. The study was registered in the Brazilian Registry of Clinical Trials: RBR-5GKNG5. RESULTS: significant difference in the microclimate variables were observed when the groups (intervention and control) and the timepoint of measurement (beginning and end of surgery) were compared. When assessing temperature, an increase (+3.3 °C) was observed with TPF and a decrease (-7.4 °C) was recorded with MPF. Regarding skin moisture, an increase in moisture (+14.6 AU) was recorded with TPF and a slight decrease (-0.3 AU) with MPF. CONCLUSIONS: The findings of this study suggest that MPF is more effective than TPF in controlling skin microclimate (temperature and moisture) in heels skin of hospitalized patients undergoing elective surgeries. However, this control should be better investigated in other studies.

Effect of Prewarming on Skin Temperature Changes After Spinal Anesthesia in Transurethral Resection of the Bladder.

PURPOSE: Monitoring of peripheral skin temperature changes is an objective and rapid method to evaluate the success of neuraxial block after spinal anesthesia. The aim of this study is to investigate the effect of prewarming on peripheral temperature changes after the administration of spinal anesthesia. DESIGN: Randomized, prospective, single-blind study. METHODS: In this study, patients scheduled for transurethral resection of the bladder surgery under spinal anesthesia were divided into two groups: those with active prewarming and those without active prewarming. The groups were compared in core and skin temperature changes after administration of spinal anesthesia, length of stay in the postanesthesia care unit, shivering score, and the thermal comfort scale. FINDINGS: A statistically significant difference was found between the groups on time for a 1 °C increase in ankle and toe skin temperatures (P < .001). There was a statistically significant difference between the groups in core temperature measurements (P < .001). When thermal comfort was compared between the groups, a statistically significant difference was found (P < .001). Patients' shivering score (P = .704), and length of stay in the postanesthesia care unit (P = .059) between the groups were similar. CONCLUSIONS: Skin temperature changes in the prewarming group were lower, and this group had a lower rate of increase than the nonprewarming group. Therefore, skin temperature changes in the lower extremity can be used to determine the success of spinal anesthesia in patients who are prewarmed, with the awareness of these differences.

Warm ears, a red flag for sleepiness?

Core body and skin temperatures are intimately linked to sleep and alertness. The distal-to-proximal skin temperature gradient has been described as a good physiological predictor for sleep onset. Increased ear skin temperature is often caused by increased blood flow reflected in redness, which is commonly noticed in people who are sleepy, especially anecdotally in children. Nonetheless, no prior study investigated the possible relation between sleepiness and ear skin temperature as a separate measurement. We assessed the relation between ear skin temperature and sleepiness in patients undergoing regular electroencephalographic examinations, because of suspicion of epilepsy, both without and after sleep deprivation. Subjective sleepiness was measured using the Stanford Sleepiness Scale, and objective sleepiness by determining sleep onset with electroencephalography. Distal, proximal and ear skin temperature were measured repeatedly using wireless measurement devices (iButtons). Forty-four adult patients were included. Ear skin temperature correlates weakly with distal skin temperature (r = 0.174, p < 0.001) and distal-to-proximal gradient (r = 0.160, p < 0.001), but not with proximal skin temperature (r = -0.001, p = 0.975). Ear skin temperature increased significantly in a subgroup of 13 patients, between 5 and 1 min before sleep onset (p = 0.002; η2  = 0.059), even though this increase was also associated with supine posture. iButtons is a valid method to measure ear skin temperature, which appears to function partly like a distal and partly like a proximal skin temperature measurement. Change in ear skin temperature is associated with sleep onset and supine posture.

The use of infrared thermography for non-invasive detection of bleeding and musculoskeletal abnormalities in patients with hemophilia: an observational study.

BACKGROUND: In patients with hemophilia (PwH), bleeding often occurs in joints and muscles, and early detection of hemorrhage is important to prevent the onset and progression of mobility impairment. Complex-Image analysis such as ultrasonography, computed tomography, and magnetic resonance imaging are used to detect bleeding. On the other hand, no simple and rapid method to detect the active bleeding has been reported. Local inflammatory responses occur when blood leaks from damaged vessels, and the temperature at the site of active bleeding could be expected to increase in these circumstances, leading to an increase in surrounding skin temperature. Therefore, the purpose of this study was to investigate whether the measurement of skin temperature using infrared thermography (IRT) can be used as a diagnostic aid to detect active bleeding. METHODS: Fifteen PwH (from 6 to 82 years old) complaining of discomfort such as pain were examined. Thermal images were obtained simultaneously at the affected sides and comparable unaffected sides. The average skin temperature of the affected side and of the unaffected side were measured. The temperature differences were calculated by subtracting the average skin temperature at the unaffected side from the affected side. RESULTS: In eleven cases with active bleeding, the skin temperature at the affected side was more than 0.3 °C higher (0.3 °C to 1.4 °C) compared to the unaffected side. In two cases without active bleeding, there were no significant differences in skin temperature between the affected and unaffected sides. In two cases with previous rib or thumb bone fracture, the skin temperature at the affected side was 0.3 °C or 0.4 °C lower than that of the unaffected side, respectively. In two cases with active bleeding in which longitudinal evaluation was conducted, the difference in skin temperature decreased after hemostatic treatment. CONCLUSION: The analysis of skin temperature deference using IRT was a useful supportive tool to readily assess musculoskeletal abnormalities and bleeding in PwH as well as to determine the success of the hemostatic treatment.

Effects of acute lower limb and trunk fatigue on balance, performance, and skin temperature in healthy males.

OBJECTIVE: It is unclear whether lower limb and trunk fatigue leads to different effects. Although some studies have compared the effects of muscle fatigue on balance and performance in healthy individuals, little is known about its effects on skin temperature. This study aimed to compare the effects of lower limb and trunk fatigue on balance, performance, and skin temperature in healthy males. METHODS: Twenty participants performed trunk and lower limb fatigue protocols on two separate days. Balance (Y-Balance Test-YBT), trunk performance (plank test), lower limb performance (Single-Leg Triple Hop-SLTH and Countermovement jump-CMJ), and skin temperature were assessed pre-fatigue and post-fatigue. Infrared Thermography assessed the skin temperatures of the trunk and lower limb. RESULTS: Compared with trunk fatigue, the lower limb fatigue protocol had a more significant adverse effect on reducing YBT score, CMJ parameters, and SLHT distance (p<0.05). Both fatigue protocols resulted in lower plank test times and trunk skin temperature (p<0.05). The changes in plank times and skin temperature were similar between protocols (p>0.05). CONCLUSIONS: Taken together, these results suggest that lower limb fatigue adversely affected balance and lower limb performance more than trunk fatigue. Trunk performance and trunk skin temperatures decreased after both fatigue protocols. Lower limb and trunk fatigue-induced changes in trunk performance and skin temperatures were similar.

Evaluation of fatigue in young female adults due to repeated exposure to heat in summer and cold in winter.

PURPOSE: The magnitude of fatigue (MF) from psychological and physiological responses during repeated exposure to heat in summer and during repeated exposure to cold in winter was evaluated to test two hypotheses on fatigue models. The first hypothesis is that exposure time (ET, min) would be a factor determining the MF and the second hypothesis is that the same fatigue models as a function of the number of exposure repetitions (NR) could be applied to both repeated exposure to heat in summer and cold in winter. METHODS: In summer, eight young adult female subjects with clothing insulation (Icl, clo) of 0.3 clo first stayed in the control room at 26 ℃ for 15 min, moved to the main testing room at 30 ℃ for 25 min, 33 °C for 15 min, or 36 ℃ for 10 min, and then returned to the control room. The product of air temperature difference (ΔTa, ℃) and ET was designed to be almost equal among these latter three conditions. The exposure was repeated five times. In winter, the same female subjects with Icl of 0.84 clo first stayed in the control room at 24 ℃ for 15 min, moved to the main testing room at 18 ℃ for 30 min, 15 ℃ for 20 min, or 12 ℃ for 15 min, and then returned to the control room. Again, the product of ΔTa and ET was designed to be equal among these latter three conditions. The exposure was repeated four times. The scores of subjective fatigue feeling (SFF) and salivary amylase value (SAV) were recorded when the subjects returned to the control room. Tympanic temperature, skin temperatures and local sweat rates (Sw, mg/cm2/min) at chest, forearm, front thigh, and front shin, and ECG were continuously monitored, except for Sw in the winter experiment. RESULTS: In the summer experiment, the SFF showed a threshold value at ΔTa = 4 ℃ but continuously increased with NR at ΔTa = 7 ℃ and 10 ℃. It was not correlated with ECG variables, but was positively correlated with SAV (R2 = 0.50) and the mean Sw (R2 = 0.76) at ΔTa = 7 ℃ and 10 ℃. In the winter experiment, the SFF showed a threshold value at ΔTa = - 6 ℃ but continuously increased with NR at ΔTa = - 9 ℃ and - 12 ℃. It was correlated with SAV at ΔTa = - 9 ℃ (R2 = 0.77) and score of LF: HF ratio at ΔTa = - 6 ℃ and - 9 ℃ (R2 = 0.49). CONCLUSION: It was confirmed that ET may be related to the MF and that different fatigue models may be applied dependent on ΔTa during repeated exposure to heat in summer and during repeated exposure to cold in winter. Thus, the two hypotheses were verified.

Central versus peripheral mechanisms of cold-induced vasodilation: a study in the fingers and toes of people with paraplegia.

PURPOSE: This study examined physiological and perceptual parameters related to cold-induced vasodilation (CIVD) in the fingers and toes of people with paraplegia and compared them with responses observed in able-bodied individuals. METHODS: Seven participants with paraplegia and seven able-bodied individuals participated in a randomized matched-controlled study involving left-hand and -foot immersion in cold water (8 ± 1 °C) for 40 min during exposure to cool (16 ± 1 °C), thermoneutral (23 ± 1 °C), and hot (34 ± 1 °C) ambient conditions. RESULTS: Similar CIVD occurrence was observed in the fingers in the two groups. In toes, three of the seven participants with paraplegia revealed CIVDs: one in cool, two in thermoneutral, and three in hot conditions. No able-bodied participants revealed CIVDs in cool and thermoneutral conditions, while four revealed CIVDs in hot conditions. The toe CIVDs of paraplegic participants were counterintuitive in several respects: they were more frequent in cool and thermoneutral conditions (compared to the able-bodied participants), emerged in these conditions despite lower core and skin temperatures of these participants, and were evident only in cases of thoracic level lesions (instead of lesions at lower spinal levels). CONCLUSION: Our findings demonstrated considerable inter-individual variability in CIVD responses in both the paraplegic and able-bodied groups. While we observed vasodilatory responses in the toes of participants with paraplegia that technically fulfilled the criteria for CIVD, it is unlikely that they reflect the CIVD phenomenon observed in able-bodied individuals. Taken together, our findings favor the contribution of central over peripheral factors in relation to the origin and/or control of CIVD.

Thermal response of human body with immersion suit in cold environment.

Hypothermia caused by cold water immersion is one of the main causes of death in marine accidents. Immersion suit is a kind of protective clothing when implementing flying tasks over the sea in cold seasons, with the main function to slow down the loss of human heat in water and prolong the survival time. In this study, the thermal properties and wearing types of immersion suit and underwear were analyzed. The subjects with internal- and external-wear immersion suit exposed to the experimental environments for 2 h in five working conditions. The core temperature, weighted average skin temperature, and average body temperature were measured and calculated. Both internal- and external-wear immersion suits could fulfil the cold protection requirements under the experimental conditions. The results of clothing parameter tests and physiological experiments both exhibit that the external-wear immersion suit has better thermal insulation effect. And the tolerance time in low-temperature water was predicted, which is crucial for effective and efficient rescue during shipwreck in adverse thermal scenarios. In future research, a comprehensive evaluation and analysis of the thermal insulation performance of immersion suit could be completed in combination with the water ingress of the clothing, the subjects' thermal comfort, and flexibility of the clothing.

Effect of air blowing inside isolated hospital clothing on perceptual and physiological heat strain in laboratory conditions.

Heat stress is one of the most common complaints of health care employees who wear isolation gowns to protect themselves from biological agents, particularly during the warmer seasons. This study was conducted in a climatic chamber to determine the influence of airflow within isolated hospital gowns on physiological-perceptual heat strain indices. The experiment was conducted in three trials: regular clothes (CON), an impenetrable gown without air blowing (GO), and a gown with air blowing (GO + FAN) at temperature conditions of 27 °C and 25% relative humidity (RH). During the trial, physiological-perceptual response data were recorded for a half-hour on a treadmill at a speed of km/hr and a slope of 0% activity at 5-min intervals. The ASHRAE Likert scale was used to assess thermal comfort (TC), thermal sensation (TS), and skin wetness sensation (WS). As the results show, there was a significant difference in mean scores for TC and WS in both sexes when working in the CON, GO, and GO + FAN groups (P < 0.001). In women, the mean scores for TS, TC, and WS reduced considerably (P < 0.001) in the GO and GO + FAN in the amount of 10 and 12 CFM (20 [Formula: see text]/h), but in males, there was a statistically significant difference between mean scores (P < 0.001) in the GO + FAN at 12 CFM (20 [Formula: see text]/h) and 14 CFM (24 [Formula: see text]/h). Also, the greatest difference between the average heart rate, chest temperature, and temperature inside the clothes in women and men in the trials GO and GO + FAN was observed in the air flow 12 CFM and 14 CFM, respectively (P < 0.001). The usage of an air blower in isolated hospital clothes has been shown to influence physiological-perceptual parameters in men and women substantially. The existence of airflow in these gowns can improve safety, performance, and thermal comfort while also decreasing the risk of heat-related disorders.