Sweat Rate Research Articles

A dataset of proteomic changes during human heat stress and heat acclimation

Hotter climates have important impacts on human health and performance. Yet, the cellular and molecular responses involved in human heat stress and acclimation remain understudied. This dataset includes physiological measurements and the plasma concentration of 2,938 proteins collected from 10 healthy adults, before and during passive heat stress that was performed both prior to and after a 7-day heat acclimation protocol. Physiological measurements included body temperatures, sweat rate, cutaneous vascular conductance, blood pressure, and skin sympathetic nerve activity. The proteomic dataset was generated using the Olink Explore 3072 assay, enabling a high-multiplex antibody-based assessment of protein changes based on proximity extension assay technology. The data need to be interpreted in the context of the moderate level of body hyperthermia attained and the specific demographic of young, healthy adults. We have made this dataset publicly available to facilitate research into the cellular and molecular mechanisms involved in human heat stress and acclimation, crucial for addressing the health and performance challenges posed by rising temperatures.

Quantifying Exercise Heat Acclimatisation in Athletes and Military Personnel: A Systematic Review and Meta-analysis.

Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat. The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel. Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6weeks were included. MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022. A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias. A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated. Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of - 0.19°C [90% CrI: - 0.41 to 0.05, Pd = 91%] and - 6beats·min-1 [90% CrI: - 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by - 0.24°C [90% CrI: - 0.67 to 0.20, Pd = 85%] and - 7beats·min-1 [90% CrI: - 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01L·h-1 [90% CrI: - 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation. Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length. CRD42022337761.

Measurement Compensation Method for Wearable Microfluidic Sweat Sensors Toward Monitoring a Wide Range of Local Sweat Rates and Electrolyte Concentration

Measurement Compensation Method for Wearable Microfluidic Sweat Sensors Toward Monitoring a Wide Range of Local Sweat Rates and Electrolyte Concentration

Comparing thermoregulatory responses between short and long moderate intensity intermittent exercise protocols with the same duty cycle

To date, the thermoregulatory response between continuous and intermittent exercises has been investigated whilst limited studies are available to examine the thermoregulatory responses between different modes of intermittent exercises. We sought to determine the effect of two patterns of short duration intermittent exercises (180:180 (3-min) and 30:30 s (30-s) work: rest) on thermoregulatory responses in a temperate environment (25 °C, 50% RH, vapor pressure: 1.6 kPa) with low airflow (0.2 m/s). Twelve male participants (Age:24.0(5.0) year; VO2max: 53(8) mL.kg−1.min−1; BSA:1.7(0.1) m2) cycled at 50% VO2max for 60 min in 3-min and 30-s intervals to result in the same 30-min net exercise duration. Core and skin temperatures, the percent increase of skin blood flow (forearm and chest) from baseline and local sweat rate (forearm and chest) were not different between 3-min and 30-s (all P > 0.35) from the onset of exercise to the end of the exercise. Similarly, the mean body temperature onsets of skin blood flow (forearm and chest) and local sweat rates (forearm and chest) were not different between different mode of intermittent exercises (all P > 0.1). Furthermore, thermal sensitivities of skin blood flow (forearm and chest) and local sweat rate (forearm and chest) with increasing mean body temperature were not different between different mode of intermittent exercises (all P > 0.1). We conclude that intermittent exercises with different work periods at moderate exercise intensity did not alter core temperature and thermoeffector responses in a temperate environment. (241/250)

Influence of Biological Sex and Fitness on Core Temperature Change and Sweating in Children Exercising in Warm Conditions.

This study aimed to investigate the associations of biological sex and aerobic fitness (i.e., V̇O 2peak ) on the change in gastrointestinal temperature (∆ Tgi ) and whole-body sweat rate (WBSR) of children exercising in warm conditions. Thirty-eight children (17 boys, mean ± SD = 13.7 ± 1.2 yr; 21 girls, 13.6 ± 1.8 yr) walked for 45 min at a fixed rate of metabolic heat production (8 W·kg -1 ) in 30°C and 40% relative humidity. Biological sex and relative V̇O 2peak were entered as predictors into a Bayesian hierarchical generalized additive model for Tgi . For a subsample of 13 girls with measured body composition, body fat percent was entered into a separate hierarchical generalized additive model for Tgi . Sex, V̇O 2peak , and the evaporative requirement for heat balance ( Ereq ) were entered into a Bayesian hierarchical linear regression for WBSR. The mean ∆ Tgi for boys was 0.71°C (90% credible interval = 0.60-0.82) and for girls 0.78°C (0.68-0.88). A predicted 20 mL·kg -1 ·min -1 higher V̇O 2peak resulted in a 0.19°C (-0.03 to 0.43) and 0.24°C (0.07-0.40) lower ∆ Tgi in boys and girls, respectively. A predicted ~13% lower body fat in the subsample of girls resulted in a 0.15°C (-0.12 to 0.45) lower ∆ Tgi . When Ereq was standardized to the grand mean, the difference in WBSR between boys and girls was -0.00 L·h -1 (-0.06 to 0.06), and a 20-mL·kg -1 ·min -1 higher predicted V̇O 2peak resulted in a mean difference in WBSR of -0.07 L·h -1 (-0.15 to 0.00). Biological sex did not independently influence ∆ Tgi and WBSR in children. However, a higher predicted V̇O 2peak resulted in a lower ∆ Tgi of children, which was not associated with a greater WBSR, but may be related to differences in body fat percent between high and low fitness individuals.

Triboelectric Nanogenerator Enabled Sweat Extraction and Power Activation for Sweat Monitoring

AbstractWearable sweat sensors can detect and monitor various substances in sweat, providing valuable information for healthcare monitoring and clinical diagnostics. Recent advances in flexible electronic technologies have enabled the development of wearable sweat sensors that can measure sweat rate and biochemical substances in real time, although several challenges remain, such as power management and sweat extraction issues. Here, a passive sweat extraction strategy as well as a self‐powered monitoring system (SEMS) is reported to be designed for sedentary individuals, i.e., elders. The SEMS system comprises a wearable triboelectric nanogenerator (TENG) for sweat extraction, a sweat‐activated battery (SAB) as the integrated power source, carbachol‐loaded iontophoresis electrodes for sweat extraction, microfluidics with biosensors for detecting physiological information in sweat, and near field communication (NFC)‐based wireless microelectronics for data communication, processing, and collection. By tapping the TENG, sedentary people can passively extract sweat based on the iontophoresis process, allowing the sensors to detect biological information in sweat. The good flexibility of the SEMS device enables real‐time and non‐invasive detection of sweat analytes in a wearable format. This system offers a new strategy of sweat collection and analysis for the elderly group, and therefore can help to understand human physiology and personalize health monitoring deeply.

Skin-Attachable Ink-Dispenser-Printed Paper Fluidic Sensor Patch for Colorimetric Sweat Analysis.

In situ analysis of sweat biomarkers potentially provides noninvasive lifestyle monitoring and early diagnosis. Quantitative detection of sweat rate is crucial for thermoregulation and preventing heat injuries. Here, a skin-attachable paper fluidic patch is reported for in situ colorimetric sensing of multiple sweat markers (pH, glucose, lactate, and uric acid) with concurrent sweat rate tracking. Two sets of fluidic patterns-multiplexed detection zones and a longitudinal sweat rate channel-are directly printed by an automated ink dispenser from a specially developed ceramic-based ink. The ceramic ink thermal-cures into an impervious barrier, confining sweat within the channels. The ceramic-ink-printed boundary achieves higher pattern resolution, prevents fluid leakage, attains pattern thermal stability, and resistant to organic solvents. The cellulose matrix of the detection zones is modified with nanoparticles to improve the color homogeneity and sweat sensor sensitivity. The sweat rate channel is made moisture sensitive by incorporating a metal-salt-based dye. The change in saturation/color of the detection zones and/or channels upon sweat addition can be visually detected or quantified by a smartphone camera. A cost-effective way is provided to fabricate paper fluidic sensor patches, successfully demonstrating on-body multiplexed evaluation of sweat analytes. Such skin wearables offer on-site analysis, meaningful to an increasingly health-conscious population.

Evaluation of thermal properties and thermoregulatory impacts of lower back exosuit using thermal manikin

As exoskeletons and exosuits rapidly transition from laboratory to practice, the thermal discomfort posed by wearing the devices is emerging as a significant challenge towards their widespread adoption. We use a thermal manikin coupled with a thermoregulation model to evaluate the thermal properties and thermophysiological impacts of such devices. We measure thermal and evaporative resistances of summer and full clothing coupled with a legacy low-back supporting exosuit and its successor that features two design alterations to improve the user's thermal comfort. We quantify the decrease in evaporative resistance provided by substantial perforation of the back portion of the updated exosuit. The thermal manikin can replicate local skin temperature decrease associated with a release of a dual-mode thigh body attachment measured during a prior human trial. Using the thermal manikin coupled with a thermoregulation model, we simulate how the updated exosuit with several levels of assumed metabolic rate reduction impacts sweat rate, skin and core temperature changes during multiple work-rest cycles in a hot and humid climate. While a large metabolic rate reduction (>15%) is required to significantly slow the core temperature increase, even a minor metabolic rate reduction (5%) could provide a substantial reduction (20%) in the sweat rate (i.e. could reduce dehydration). Results suggest that thermal manikins with a thermoregulation model are an effective and efficient platform for comparing exosuit design features and for improving their thermal aspects. Our study highlights the comprehensive method and importance of considering thermal aspects when designing exosuits for occupational use.

Conductometric Flexible CuO-Based Sweat-Loss Monitoring Sensor for Future Wearable Technology in Healthcare.

Healthcare tracking supports early diagnosis of illnesses, real-time tracking of the impacts of therapy and treatment, and tracking of cases of human health. Based on this, real-time tracking of sweat loss provides an easy, convenient, and noninvasive approach to the early diagnosis of physical illness in individuals. To date, copper oxide (CuO) as a nanostructured semiconductor metal-oxide is regarded as a hopefully p-type sensing material. The corresponding sweat rate monitoring systems were fabricated using a repeatable and cost-effective SILAR system using a cellulose acetate-based organic substrate. To provide a practical application, we investigated the working efficiency of Al:CuO under room conditions since most clinical and healthcare industries operate under ambient temperature. Fabricated flexible devices immediately respond to the implementation of the sweat solution and reach a steady-state value in a short time. It can be obtained from experimental results that the sweat-loss monitoring performances of CuO-based devices can be enhanced by employing Al-doping. The increment in the sensing efficacy was interpreted in terms of structural and morphological characterization and electrical data. Our designed flexible thin film-based system can be used in conjunction with a customized wearable, healthcare industry integrated, low-cost fabrication source.

The reliability of a portable steam sauna pod for the whole-body passive heating of humans

IntroductionPassive heating is receiving increasing attention within human performance and health contexts. A low-cost, portable steam sauna pod may offer an additional tool for those seeking to manipulate physiological (cardiovascular, thermoregulatory and sudomotor) and perceptual responses for improving sporting or health profiles. This study aimed to 1) report the different levels of heat stress and determine the pods’ inter-unit reliability, and 2) quantify the reliability of physiological and perceptual responses to passive heating. MethodIn part 1, five pods were assessed for temperature and relative humidity (RH) every 5 min across 70 min of heating for each of the 9 settings. In part 2, twelve males (age: 24 ± 4 years) completed two 60 min trials of passive heating (3 × 20 min at 44 °C/99% RH, separated by 1 week). Heart rate (HR), rectal (Trectal) and tympanic temperature (Ttympanic) were recorded every 5 min, thermal comfort (Tcomfort) and sensation (Tsensation) every 10 min, mean arterial pressure (MAP) at each break period and sweat rate (SR) after exiting the pod. ResultsIn part 1, setting 9 provided the highest temperature (44.3 ± 0.2 °C) and longest time RH remained stable at 99% (51±7 min). Inter-unit reliability data demonstrated agreement between pods for settings 5–9 (intra-class correlation [ICC] >0.9), but not for settings 1–4 (ICC <0.9). In part 2, between-visits, high correlations, and low typical error of measurement (TEM) and coefficient of variation (CV) were found for Trectal, HR, MAP, SR, and Tcomfort, but not for Ttympanic or Tsensation. A peak Trectal of 38.09 ± 0.30 °C, HR of 124 ± 15 b min−1 and a sweat loss of 0.73 ± 0.33 L were reported. No between-visit differences (p > 0.05) were observed for Trectal, Ttympanic, Tsensation or Tcomfort, however HR (+3 b.min−1) and MAP (+4 mmHg) were greater in visit 1 vs. 2 (p < 0.05). ConclusionPortable steam sauna pods generate reliable heat stress between-units. The highest setting (44 °C/99% RH) also provides reliable but modest adjustments in physiological and perceptual responses.

Stress Monitoring Using Machine Learning, IoT and Wearable Sensors.

The Internet of Things (IoT) has emerged as a fundamental framework for interconnected device communication, representing a relatively new paradigm and the evolution of the Internet into its next phase. Its significance is pronounced in diverse fields, especially healthcare, where it finds applications in scenarios such as medical service tracking. By analyzing patterns in observed parameters, the anticipation of disease types becomes feasible. Stress monitoring with wearable sensors and the Internet of Things (IoT) is a potential application that can enhance wellness and preventative health management. Healthcare professionals have harnessed robust systems incorporating battery-based wearable technology and wireless communication channels to enable cost-effective healthcare monitoring for various medical conditions. Network-connected sensors, whether within living spaces or worn on the body, accumulate data crucial for evaluating patients' health. The integration of machine learning and cutting-edge technology has sparked research interest in addressing stress levels. Psychological stress significantly impacts a person's physiological parameters. Stress can have negative impacts over time, prompting sometimes costly therapies. Acute stress levels can even constitute a life-threatening risk, especially in people who have previously been diagnosed with borderline personality disorder or schizophrenia. To offer a proactive solution within the realm of smart healthcare, this article introduces a novel machine learning-based system termed "Stress-Track". The device is intended to track a person's stress levels by examining their body temperature, sweat, and motion rate during physical activity. The proposed model achieves an impressive accuracy rate of 99.5%, showcasing its potential impact on stress management and healthcare enhancement.

Repeatability of Ad Libitum Water Intake during Repeated 1 h Walking/Jogging Exercise Sessions Conducted under Hot Ambient Conditions.

A drinking strategy aiming to replace a given percentage of the sweat losses incurred during exercise should result in reproducible fluid intake volume and, hence, fluid balance from one exercise session to the other performed under similar scenarios. Whether this may also be the case with ad libitum drinking during exercise is unclear. We characterized the repeatability of ad libitum water intake during repeated 1 h exercise sessions and examined its effect over time on fluid balance and selected physiological functions and perceptual sensations. Twelve (3 women) healthy individuals participated in this study. At weekly intervals, they completed four 2 × 30 min walking/jogging exercise bouts (55% V˙O2max, 40 °C, 20-30% relative humidity) interspersed by a 3 min recovery period. During exercise, participants consumed water (20 °C) ad libitum. There were no significant differences among the four exercise sessions for absolute water intake volume (~1000 mL·h-1), percent body mass loss (~0.4%), sweat rate (~1300 mL·h-1) and percent of sweat loss replaced by water intake (~80%). Heart rate, rectal temperature, and perceived thirst and heat stress did not differ significantly between the first and fourth exercise sessions. Perceived exertion was significantly lower during the fourth vs. the first exercise session, but the difference was trivial (<1 arbitrary unit). In conclusion, ad libitum water intake during four successive identical 1 h walking/jogging sessions conducted in the heat will result in similar water intake volumes and perturbations in fluid balance, heart rate, rectal temperature, and perceived thirst, heat stress and exertion.

Evidence of seasonal heat acclimatisation in recreationally active adults during a mild summer

ObjectivesTo assess the magnitude of seasonal heat acclimatisation in recreationally active adults and contextualise the process by documenting the factors that influence adaptations. DesignLongitudinal, repeated measures design. MethodsSeventeen (7 females) recreationally active adults (28 ± 8 yr, V̇O2peak 54 ± 8 mL·kg−1·min−1) exercising outdoors a minimum of 5 h·wk−1 completed a 45-min heat response test running at 60 % V̇O2peak in 40 °C and 30 % relative humidity prior to, midway through, and following summer. Self-reported physical activity diaries were completed at the beginning and end of summer. Daytime wet-bulb globe temperature was calculated for each day of summer. Data were analysed using Bayesian ordinal regressions. ResultsDaytime wet-bulb globe temperature was 22.0 ± 4.4 °C, with the most common hour for recreational exercise being 17:00 to 18:00. Following summer, the rise in oesophageal temperature and mean skin temperature during the heat response test was lower by 0.12 °C [90 % credible interval: −0.30, 0.06; probability of direction = 87 %] and 0.43 °C [−0.74, −0.10; 98 %], respectively. Moreover, forearm local sweat rate increased by 0.26 mg·cm−2·min−1 [0.15, 0.36; 100 %]. There was minimal evidence of a change in the increase in heart rate (1 beat·min−1 [−3, 5; 62 %]), or whole-body sweat rate (0.03 L·h−1 [−0.11, 0.15; 68 %]) during the heat response test. ConclusionsAlthough there was evidence of partial heat adaptation in recreationally active adults following summer, a combination of exercising later in the day and the prevailing environmental conditions (La Niña in South-Eastern Australia) may have blunted the development of further adaptations.

Effect of voluntary electric fan use on autonomic and perceptual responses to lower leg passive heating in humans

This study investigated the efficacy of voluntary fan utilization on autonomic thermoeffector responses and thermal perceptions during passive heating by lower leg immersion (42 °C) in a 27 °C ambient temperature, 50% relative humidity. Fourteen young healthy adults (8 females) were recruited for this study where they underwent two trials with (Fan) and without an electric fan (No fan) during 50 min of passive heat stress. The skin temperature on forearm and abdomen was lower in Fan than in No fan (all p < 0.02), and the local skin temperature on the chest, and mean skin temperature were significantly lower in Fan than in No fan in the final 20 min (mean value of mean skin temperature: 34.77(0.15) °C vs 35.11(0.12) °C, respectively, all p < 0.03), whilst the rectal temperature was not different between trials (37.11(0.23) °C vs 37.08(0.27) °C, p = 0.78). The sensitivity of local sweat rate (LSR) with the increase of mean body temperature on the chest and forearm was significantly lower in Fan than No fan trials (all p < 0.02). The sum value of thermal sensation was lower and wetness was higher in Fan than in No fan in the final 25 min (thermal sensation: 7.50 (1.25) vs 5.00 (3.06), wetness: −6.57 (2.31) vs −5.21 (2.46), all p<0.03) whilst thermal discomfort did not differ significantly between trials (p = 0.12). The voluntary use of an electric fan attenuates the autonomic thermoeffector response, such as sweating, and influences thermal sensation and wetness but did not affect core temperature and thermal discomfort during lower leg immersion.

Thermoregulatory and perceptual implications of varying torso soft armour coverage during treadmill walking in dry heat

Modular armour allows soldiers to adjust the level of coverage according to the threat level. We hypothesized that armour configurations with lower levels of torso soft armour coverage attenuate physiological and perceptual responses during exercise in the heat. Fifteen adults (5 females/10 males, 26 ± 5 years) walked (5 km/h, 1% incline, 1h) in dry heat (38 °C, 20% humidity) while wearing body armour that provided; i) high coverage (HC: 0.57 ± 0.09 m2, 18.5 ± 0.3 kg), ii) moderate coverage (MC: 0.44 ± 0.07 m2, 18.1 ± 0.3 kg), iii) low coverage (LC1: 0.21 ± 0.03 m2, 17.4 ± 0.1 kg), or iv) low coverage with weight equalization (LC2: 0.21 ± 0.03 m2, 18.6 ± 0.2 kg). Core temperature (Tcore), heart rate (HR), metabolic heat production (M-W), whole-body sweat rate (WBSR), and perceptual responses were measured. M-W during exercise (629 ± 126 W) did not differ between configurations (p = 0.30). The change in Tcore (HC: 0.88 ± 0.37 °C, MC: 0.85 ± 0.32 °C, LC1: 0.91 ± 0.38 °C, LC2: 0.89 ± 0.42 °C, p = 0.93), HR (HC: 97 ± 14 bpm, MC: 103 ± 16 bpm, LC1: 96 ± 15 bpm, LC2: 97 ± 20 bpm, p = 0.08), and WBSR (HC: 10.2 ± 3.4 g/min, MC: 10.3 ± 4.3 g/min, LC1: 9.9 ± 4.7 g/min, LC2: 10.4 ± 4.5 g/min, p = 0.84) did not differ between configurations. Perceptual responses did not differ between configurations (all p ≥ 0.15). Reducing torso soft armour coverage, with minimal reductions in armour load, does not reduce physiological or perceptual strain during walking in dry heat.

Efficacy of 5% sofpironium bromide gel in Duchenne muscular dystrophy with palmoplantar hyperhidrosis: A retrospective case study.

Duchenne muscular dystrophy (DMD) is a severe, progressive, muscle-wasting disease. Notably, several extramuscular manifestations and complications of advanced DMD, including skin disorders, are known. However, hyperhidrosis and its treatment have not been well-described in association with advanced DMD, therefore we aimed to confirm the efficacy of 5% sofpironium bromide gel in treating secondary hyperhidrosis in patients with advanced DMD. We retrospectively reviewed patients with advanced DMD who underwent treatment with 5% sofpironium bromide gel. All patients were evaluated using the hyperhidrosis disease severity scale (HDSS) score and by measuring the gravimetric weight of palmar and/or plantar sweat. Three patients with advanced DMD were treated and the patients were aged 28, 31, and 32 years, respectively. Their HDSS scores showed a decreasing tendency within 5 weeks after treatment. In addition, all patients had a decreased gravimetric weight of palmar and/or plantar sweat, and the mean decrease rate of palmar sweat at 7 weeks after treatment was 53.7%. One patient had skin dryness on both soles, but no serious adverse events were observed. Treatment using 5% sofpironium bromide gel showed beneficial efficacy against palmoplantar hyperhidrosis in patients with advanced DMD. These findings warrant further investigation in future studies.

Reexamining the Minimum Sweat Rate Requirement for Sweat Chloride Testing.

Guidelines for sweat chloride testing endorse a minimum sweat rate for reporting results. Bilateral sweat collection is recommended, but if both sites fail to meet the minimum rate (quantity not sufficient, QNS), the test should be repeated. In this study, we examine the correlation between sweat rate and sweat chloride concentration ([Cl-]), assess the accuracy of specimens collected at suboptimal rates, and investigate the use of pooled bilateral specimens for chloride measurement. Pearson correlation was employed to analyze the relationship between sweat rate and chloride concentration, [Cl-], in 674 macroduct collections. Weighted kappa was evaluated to determine cystic fibrosis (CF) diagnostic classification concordance for 18 tests with paired arms above vs below the minimum sweat rate. Deming regression was applied to compare [Cl-] from pooled bilateral specimens vs neat specimens in 27 collections with residual volume available after clinical testing. Pearson correlation of sweat rate vs [Cl-] was minimal (r = -0.0735) across specimens with varying rates and [Cl-]. There was substantial agreement in CF diagnostic classification between arms for bilateral collections with discordant sweat rates. Regression analysis of [Cl-] in pooled vs nonpooled specimens revealed a slope of 0.984 and an intercept of 0.796. Negligible correlation of sweat rate and [Cl-] suggests the minimum sweat rate for macroduct collectors may be overly stringent. Reporting of [Cl-] in specimens with ≥10 µL (rate ≥0.3 µL/min) may reduce QNS rates without compromising diagnostic accuracy. Preliminary data suggests pooling of bilateral collections may be a feasible option to achieve the required volume for testing.

A-332 Sweat rate does not influence sweat chloride concentration

Abstract Introduction The recommendations for sweat chloride ([Cl-]) testing from the Clinical and Laboratory Standards Institute (CLSI C34-A4 2019) endorse a minimum sweat rate of 1g/m2/min to validate efficient sweat stimulation. For labs that use macroduct ® collection devices, this rate corresponds to a sweat volume ≥15 µL collected within a 30-minute period. Bilateral collection and testing is also advised to improve the odds of obtaining a sufficient specimen from at least 1 site. When both sites fail to meet the minimum rate, the test is invalid (QNS) and should be repeated, potentially delaying Cystic Fibrosis (CF) diagnosis. In this study, we evaluate the premise for the minimum sweat rate by investigating the relationship between sweat rate and [Cl-]. In a sub-analysis, residual sweat available after clinical testing is used to examine the effect of specimen pooling on [Cl-]. This study has the potential to inform best practices for future sweat testing guidelines, decrease QNS rates, and reduce time to CF diagnosis. Methods Thirteen months of data from sweat tests performed at St. Louis Children's Hospital were reviewed. All collections were performed using macroduct devices following CLSI 34-A4 guidelines (results from QNS specimens were not reported clinically). Pearson correlation was calculated to examine the relationship between sweat rate and [Cl-] (n = 354). Deming regression was applied to evaluate the effect of specimen pooling, versus results from individual sites, in 19 collections with residual volume after clinical testing. Results Figure 1 Conclusion Negligible correlation between rate and [Cl-] across a wide range of values suggests the current minimum volume for macroduct collections (15 µL) may be overly stringent. Reporting of [Cl-] in specimens with ≥10 µL sweat may decrease QNS rates without compromising accuracy. Preliminary data suggests pooling of bilateral collections may be a feasible option to achieve the minimum volume required for testing (10 µL).

Sequential biofluid sampling microfludic multi-sensing patch for more accurate sweat analysis under sedentary condition

Wearable sweat sensors hold immense potential for continuous monitoring of physiological parameters non-invasively. However, environmental and physiological changes may lead to reduced sweating, making iontophoresis-induced sweat analysis a more attractive and feasible option for easy-sampling in daily life. Nevertheless, this approach also faces challenges such as analyte concentration being affected by sweat rate variance and sweat dilution. To address these challenges, we have developed a multi-sensing patch for iontophoresis-stimulated sweat detection under sedentary conditions. The platform integrated electrochemical sensor arrays with microfluidic components for a rapid collection and in situ measurement including metabolites (glucose and ethanol) and electrolytes (Na+ and pH) in sweat. The designed microfluidic patch, capable of sequential sweat collection, significantly improved the signal stability at low sweat rate and its performance was verified by software simulation, in vitro analysis, and on-body signal monitoring. Overall, this microfluidic sensing patch opens an exciting avenue for analyzing the perspiring condition of sedentary individuals, making it an attractive option for point-of-care testing applications.

Sweat Analysis-Based Fatigue Monitoring during Construction Rebar Bending Tasks

This study proposes a novel approach to monitor the fatigue levels of construction rebar benders by measuring chemical biomarkers using sweat sensors. Fatigue resulting from dehydration and energy depletion can severely endanger the safety and health of construction workers. Sodium, lactate, glucose, and sweat rate were chosen as detectable biomarkers in this study, as their concentrations can indicate hydration status, energy consumption, and electrolyte balance, making them suitable for fatigue monitoring. The results were used to construct a fatigue model using supervised machine learning approaches. Construction rebar experiments were conducted while the sweat-based biosensors were applied to rebar workers to evaluate their fatigue with five different classifiers, demonstrating accuracy rates ranging from 71.43% to 96.43%. The results suggested that sweat-based biomarkers offer a noninvasive and accessible fatigue monitoring alternative. This can potentially help alleviate fatigue-related adverse ill effects like dehydration or cramping by enabling instant fluid or nutrient supply recommendations during construction manual tasks. It also provides valuable insights into the physiological effects of rebar work. Besides, this study presents a valuable model for predicting workers’ fatigue levels, which could be applied in the construction industry to improve workers’ safety and productivity. Furthermore, the study highlights the importance of maintaining appropriate hydration, nutrition, and electrolyte balance during physically demanding tasks like construction manual work.Practical ApplicationsThe study demonstrates that sweat biomarkers, including sweat rate, sodium, lactate, and glucose, can be utilized to assess fatigue among construction rebar workers. Sweat biosensors offer advantages of small size and non-invasiveness, making them suitable for a wide range of scenarios in both the construction industry and sports fields. Moreover, sweat rate and sodium levels can indicate hydration status, and their measurements can be used to recommend immediate fluid intake. Also, lactate and glucose are essential resources that sustain the body, and their measurements can suggest appropriate nutritional intake. These instant recommendations can alleviate the adverse effects of fatigue, consequently reducing fatigue levels. Thus, it is a promising methodology for enhancing the health and safety of the construction industry. In addition, the results of the study will be shared with construction companies, allowing them to introspect fatigue development and chalk out further interventions and policies to manage fatigue effectively.