Sweat Rate Research Articles

Demonstration of a Validated Direct Current Wearable Device for Monitoring Sweat Rate in Sports

Sweat rate magnitude is a desired outcome for any wearable sensing patch dedicated to sweat analysis. Indeed, sweat rate values can be used two-fold: self-diagnosis of dehydration and correction/normalization of other physiological metrics, such as Borg scale, VO2, and different chemical species concentrations. Herein, a reliable sweat rate belt device for sweat rate monitoring was developed. The device measures sweat rates in the range from 1.0 to 5.0 µL min−1 (2 to 10 µL min−1 cm−2), which covers typical values for humans. The working mechanism is based on a new direct current (DC) step protocol activating a series of differential resistance measurements (spatially separated by 800 µm) that is gradually initiated by the action of sweat, which flows along a customized microfluidic track (~600 µm in width, 10 mm in length, and 235 µm in thickness). The device has a volumetric capacity of ~16 µL and an acquisition frequency between 0.010 and 0.043 Hz within the measured sweat rate range. Importantly, instead of using a typical and rather complex AC signal interrogation and acquisition, we put forward the DC approach, offering several benefits, such as simplified circuit design for easier fabrication and lower costs, as well as reduced power consumption and suitability for wearable applications. For the validation, either the commercial sweat collector (colorimetric) or the developed device was performed. In five on-body tests, an acceptable variation of ca. 10% was obtained. Overall, this study demonstrates the potential of the DC-based device for the monitoring of sweat rate and also its potential for implementation in any wearable sweat platform.

Partial involvement of nitric oxide synthase in increased pilocarpine-induced sweating in exercise-trained men

The physiological mechanisms involved in augmented cholinergic agonist-induced sweating in exercise-trained individuals remain unclear. This study hypothesizes that nitric oxide synthase (NOS) contributes to augmented pilocarpine-induced sweating in habitually exercise-trained individuals. Endurance-trained and untrained men (n=15 each) iontophoretically received 1% L-NAME, a NOS inhibitor, and saline (control) in the forearm and then administered 0.001% and 1% pilocarpine to evaluate sweat rate. L-NAME administration attenuated pilocarpine-induced sweating by 10% in the exercise-trained (P = 0.004) but not in untrained (P = 0.764) groups independent of pilocarpine concentrations. Results indicate that NOS partially contributes to increased cholinergic sweating in exercise-trained men.

Estimation of the Number of Active Sweat Glands Through Discrete Sweat Sensing

Sweat is a biomarker-rich fluid with potential for continuous patient monitoring via wearable devices. However, biomarker concentrations vary with the sweat rate per gland, posing a challenge for sweat sensing. To address this, we propose an algorithm to compute both the number of active sweat glands and their individual sweat rates. We developed models of sweat glands and a discrete sweat-sensing device to sense sweat volume. Our algorithm estimates the number of active glands by decomposing the signal into patterns generated by the individual sweat glands, allowing for the calculation of individual sweat rates. We assessed the algorithm’s accuracy using synthetic datasets for varying physiological parameters (sweat rate and number of active sweat glands) and device layouts. The results show that device layout significantly affects accuracy, with error rates below 0.2% for low and medium sweat rates (below 0.2 nL min−1 per gland). However, the method is not suitable for high sweat rates. The suitable sweat rate range can be adapted to different needs through the choice of device. Based on our findings, we provide recommendations for optimal device layouts to improve accuracy in estimating active sweat glands. This is the first study to focus on estimating the sweat rate per gland, which essential for accurate biomarker concentration estimation and advancing sweat sensing towards clinical applications.

Intrinsic versus extrinsic contribution to intraindividual sweat rate variability of individual eccrine glands

The purpose of the current study was twofold. First, to determine the intraindividual variability of sweat rate per gland for a given skin location during exercise in the heat. Second, to determine the relative importance of intrinsic vs. extrinsic factors as the source of the intraindividual variability in sweat rate per gland. Sweat rate of individual eccrine glands on the forearm was measured following pilocarpine iontophoresis and during exercise in the heat. In five participants during exercise in the heat the measured sweat rate for individual forearm eccrine glands (n = 500) ranged from 0.5 nL/gland/min to 16 nL/gland/min, or over a 30-fold difference. The mean (SD) intraindividual coefficient of variation in sweat rate per gland was 36 (5)% and 49 (10)% (p = 0.008) following pilocarpine iontophoresis and during exercise in the heat, respectively. Such results suggest that intrinsic factors (i.e., sweat gland size and cholinergic sensitivity) contribute approximately three times more than extrinsic factors (i.e., sweat gland nerve fiber density and threshold amplitude) towards explaining the large intra-person variability in sweat rate per gland seen during exercise in the heat.

The Effect of a Synthetic-Grass Sport Surface on Physiology and Perception During Intermittent Exercise in Hot Conditions.

The current study aimed to determine the effect of a synthetic-grass sport surface on core body temperature, skin temperature, heart rate, thermal sensation, thermal comfort, and rating of perceived exertion (RPE)during intermittent exercise in hot conditions. Using a randomized crossover design, 13 trained/developmental team-sport athletes completed two 50-minute standardized intermittent running protocols on a synthetic and anatural-grass surface, on separate days (control-condition air temperature 32.6 °C [1.3 °C], relative humidity 43.2% [5.3%]). Final skin temperature was significantly higher on synthetic compared with natural grass at the calf (40.1 °C [2.5 °C] vs 33.4 °C [0.6 °C]; P < .001), shoulder (36.6 °C [1.7 °C] vs 33.7 °C [0.7 °C]; P < .001), and chest (33.2 °C [1.1 °C] vs 31.8 °C [1.2 °C]; P = .02). Thermal sensation (median: 2.3; interquartile range [0.5] vs 2.2 [0.5], P = .03) and sweat rate (1.5 [0.4]L·h-1 vs 1.2 [0.3]L·h-1; P = .02) were also significantly higher on synthetic grass. While final core body temperature was significantly higher on the natural than synthetic grass (38.4 °C [0.3 °C] vs 38.2 °C [0.4 °C]),there were no significant differences in delta core temperature, as well as heart rate, thermal comfort, or RPE. Higher skin temperatures, thermal sensation, and sweat rates suggest that exercising on synthetic grass in hot conditions may increase some markers of heat strain during exercise. However, delta core body temperature, heart rate, thermal comfort, and RPE remained unaffected.

Heat Strain in Different Hot Environments Hiking in Wildland Firefighting Garments.

Wildland firefighters can work at high intensity in hot environments for extended periods of time. The resulting heat strain may be modified by the environmental conditions (i.e., ambient temperature and humidity [RH]) even at equal wet-bulb globe temperatures. This investigation assessed if a hot and dry condition would create greater strain than moderate and high humidity at equivalent wet-bulb globe temperature (28°C). Twelve participants (age 24±2 y) walked at 40-50% maximum aerobic capacity for 90 and 40 min separated by a 20 min rest in dry (40°C, 20% RH), moderate-humidity (34°C, 50% RH), and high-humidity (29°C, 90% RH) conditions wearing fire resistant jacket, pants, gloves, and helmet with the neck and face exposed. Peak core temperature was higher in moderate-humidity (38.9±0.2°C, p=0.01) and high-humidity (38.9±0.6°C, p<0.01) than dry condition (38.5±0.3°C). Average net heat gain was less in dry (33±22 W) compared to moderate-humidity (38±23 W, p<0.01) and high-humidity (39±28 W, p<0.01). Peak heart rate (174±14 bpm, p=0.94), Physiological Strain Index (7.7±1.4 score, p=0.99), perceived exertion (8±2 rating, p=0.97), and Perceptual Strain Index (7.3±1.6 score, p=0.99) were not different in high-humidity compared to the dry condition (167±19 bpm, 6.9±1.3 score, 6±2 rating, 7.3±1.7 score, respectively). Whole-body sweat rate (15±6 mL/min, p=0.58) and thermal sensation (7±1 rating, p=0.37) were not different. Hiking in a humid condition while wearing protective garments creates greater exertional heat strain compared to a dry condition of equivalent wet-bulb globe temperature. Wildland firefighters should consider extra strategies to mitigate hyperthermia when humidity is high.

Effectiveness of heat stress interventions among outdoor workers: a protocol paper

IntroductionHeavy work in scorching temperatures can cause dehydration and heat stress, which can lead to a number of heat-related diseases. Heavy work in intense heat without rest or hydration is the main cause. The “Water, Rest, Shade” (WRS) intervention program for outdoor workers in hot weather reduces heat stress.MethodsThis study follows a quasi-experimental design involving 250 outdoor workers from both agriculture and brick kilns. To assess the environmental heat exposure levels, Quest Temp 3 M WBGT Monitor will be used. Tympanic temperature, Heart rate (HR), Sweat rate (SwR), and Urine specific gravity (USG) to assess the physiological responses to heat exposure using standard protocols. Blood samples will be collected to measure serum creatinine and calculate Glomerular filtration rate (GFR), and urine samples to measure pH, leucocytes, proteinuria, and hematuria. Then administer a validated and modified HOTHAPS questionnaire to capture the perception data. After the baseline assessments, Categorize the workers into two groups based on the selection criteria and the participants’ willingness. Then provide a week-long WRS intervention to the intervention group (IG). The non-intervention group will collect the same data without any intervention to assess the efficacy of the intervention by comparing both groups and measuring outcome indicators.Expected outcomeThe study will generate much-needed information to raise awareness of the importance of heat stress prevention for outdoor workers.ConclusionThis study will demonstrate the effectiveness of an intervention, provide much-needed strategies for reducing heat stress, assess both health impacts and implementation quality, and design comprehensive workplace and labor laws aim to minimise risks to millions of unorganised outdoor workers health.

A Fully Printable and Integrated System with Long-Term Stability for Versatile and Multimodal Perspiration Tracking.

Real-time and continuous monitoring of physiological status via noninvasive sweat sensing shows promise for personalized healthcare and fitness management. However, the largely varied perspiration rates in different body statuses introduce challenges for effective sweat collection and accurate sensing. Herein, a fully printable strategy was developed to realize fully integrated patches for wireless sensing of sweat biomarker levels and perspiration rates with desirable stability and versatility. The printable calcium sensors with modified ion-selective membranes displayed an ultrawide linear range of 0.1-100 mM and a long-term stability with minimized drift down to 0.083 mV/h for around 40 h. Moreover, the microfluidic channels in versatile configurations were capable of a minimum sweat rate monitoring of 0.5 μL/min and a large sweat storage volume of up to 200 μL. The as-proposed fully printable sensing platforms provide high compatibility for sensor integration to achieve versatile perspiration tracking and comprehensive health monitoring.

An effective approach for correlating Na+ concentrations with sweating rates in wearable sweat sensing platform

Accurately correlating the sweating rate and the concentration of biomarkers in sweat is essential in many sweat-based diagnostic applications. These two measurements are always done simultaneously in wearable sweat sensing platforms. However, concentration measurements of biomarkers are always delayed on the timeline compared with their production, whereas there is no such delay for sweating rate. Thus, a timeline mismatch exists between these two measurements. This means that the concentration vs rate correlation constructed on the basis of such measurements will deviate from the actual correlation. This study demonstrates the existence of this mismatch and explains its cause using sweat Na+ measurements. It also proposes an effective approach that applies a point-by-point compensation for the delay between Na+ measurements and the real-time sweating rates, such that the data on the repositioned concentration vs time curve correspond to exactly the same point on the timeline as their production. A vison sensor is developed to measure the sweating rate with high accuracy at a frequency of more than 0.1 Hz. Off-body and on-body measurements of sweating rate and Na+ concentration are carried out, and concentration–rate correlations are constructed using both measured and repositioned concentration curves. The least squares and random forest methods are employed to fit the constructed correlations and evaluate the reliability of the proposed approach. The use of the repositioned concentration curve gives a constructed correlation that is much closer to the actual one. This study indicates the necessity to rearrange sensor-measured biomarker concentration vs time curves when correlations of concentration with sweating rate need to be constructed and proposes a practical point-by-point data repositioning strategy for doing so. The results presented here will benefit the study of sweat biomarkers with unclear correlations with sweating rate, as well as providing a basis for the development of more reliable sweat-based diagnostic methods.

Multi-inspired bump-liked medical protective clothing for effectively profuse perspiration management

Janus medical protective clothing (MPC) with asymmetric wetting properties can enhance the comfort of healthcare workers by transporting sweat from the skin to exterior surfaces. However, these textiles fail to promptly remove heavy sweat (e.g., several liters), resulting in soaked fabrics and reduced comfort. Herein, inspired by superabsorbent polymers (SAPs) and lotus leaves, we propose a bump-liked MPC (BPC) for profuse perspiration management. The fabrics can enable unidirectional sweat transport through the inner Janus fabric layer and sustained absorption of large amounts of sweat by the median layer of SAPs. The bump-liked structure can store SAPs and adapt them to swelling. An external polydimethylsiloxane (PDMS)-coated layer can effectively block water, blood, and ethanol from penetrating the skin (synthetic blood contact angle, 118°; anti-blood penetration resistance, 4.8 kPa), thereby ensuring excellent protective properties. More importantly, BPC possesses an unrivalled sweat removal rate of 5.9 ml cm−2 min−1, which is three orders of magnitude higher than the human sweat rate during high-intensity exercise. This work addresses the dual challenge of profuse perspiration management and resistance to liquid penetration, which represents a promising direction for improving the thermal-moisture comfort of medical protective clothing.

Whole body sweat rate prediction: indoor treadmill and cycle ergometer exercise.

This article describes the development and validation of accurate whole body sweat rate prediction equations for individuals performing indoor cycle ergometer and treadmill exercise, where power output can be measured or derived from simple inputs. For cycle ergometry, 112 trials (67 participants) were used for model development and another 56 trials (42 participants) for model validation. For treadmill exercise, 171 trials (67 participants) were used for model development and another 95 trials (63 participants) for model validation. Trials were conducted over a range of dry-bulb temperature (20°C to 40°C), relative humidity (14% to 60%), and exercise intensity (∼40% to 85% of peak aerobic power) conditions, which were matched between model development and model validation. Whole body sweat rates were measured, and proprietary prediction models were developed (accounting for all relevant biophysical factors) and then validated. For model validation, mean absolute error for predicted sweating rate was 0.01 and 0.02 L·h-1 for cycle and treadmill trials, respectively. The 95% confidence intervals were modest for cycle ergometer (+0.25 and -0.22 L·h-1) and treadmill exercise (+0.33 and -0.29 L·h-1). The accounted for variance between predicted and measured values was 92% and 78% for cycle and treadmill exercise, respectively. Bland-Altman analysis indicated that zero and one predicted value exceeded the a priori acceptable level of agreement (equivalent to ±2% of total body mass in 3 h) for cycle and treadmill exercise, respectively. There were fewer trials with female subjects, but their values did not differ from those expected for males. This is the foremost study to develop and validate whole body sweat rate prediction equations for indoor treadmill and cycle ergometer exercise of moderate to high intensity. These prediction equations are publicly available for use (https://sweatratecalculator.com).NEW & NOTEWORTHY This study presents the development of new proprietary whole body sweat rate prediction models for people exercising indoors on a cycle ergometer or treadmill using simple input parameters and delivered through a publicly available online calculator: https://sweatratecalculator.com. In an independent validation group, the predictive models for both indoor cycling and treadmill exercise were accurate across moderate to high exercise intensities in temperate to hot conditions. These equations will enable individualized hydration management during physical training and exercise physiology experiments.

Self-powered microfluidic-based sensor for noninvasive sweat analysis

This study introduces a novel self-powered, microfluidic sweat sensing system. The device features a flexible thermoelectric system that enables efficient on-demand sweat extraction and data transmission. Both the thermoelectric generator (TEG) and the microfluidic system are thoroughly evaluated through numerical simulations and experimental testing. The device integrates electrochemical sensors for glucose, pH, and ion detection, along with solid-liquid triboelectric nanosensors to measure sweat rate. It demonstrates high selectivity for target analytes. Sweat, extracted via iontophoresis with carbagel, interacts with electrodes coated with ion-selective membranes (ISM) and glucose oxidase, producing an open-circuit potential. This selective detection of analytes results in distinct output differences. Additionally, the device delivers stable results within 20 minutes, reducing analysis time while maintaining a strong correlation with blood biomarker concentrations. This partially flexible, noninvasive system has potential applications in monitoring electrolyte loss and glucose imbalances through sweat.

Implementation of a mixed-methods heat acclimation programme in a professional soccer referee before the 2022 FIFA world cup in Qatar: a case study

ObjectivesThis case study reports the real-world practicalities of implementing a mixed-methods heat acclimation (HA) programme before the 2022 FIFA World Cup.MethodsOne male English soccer referee (age: 44 years; height: 1.82...

Bioelectrical Impedance Vector Analysis (BIVA) for Assessment of Hydration Status: A Comparison between Endurance and Strength University Athletes.

Athletic performance is greatly impacted by hydration status. The combination of several techniques is recommended to accurately measure water losses and gains. The aim of this study is to assess the validity of bioelectrical impedance vector analysis (BIVA) as a tool for measuring hydration status in endurance and strength athletes. A total of 148 athletes were evaluated on one experimental day, pre- and post-training. Urine samples were collected and analyzed for color and specific gravity. Body weight changes were measured, sweat rate was calculated, and BIVA was performed. Reference ellipses were plotted using data of 200 healthy non-athletic individuals. A moderate significant agreement was noted between raw bioelectrical values and urine specific gravity (USG) (p > 0.05). The sensitivity of classic BIVA in detecting minor changes in hydration status is confirmed both graphically and statistically. R/h and Z statistically significantly decreased post-training. Male athletes exhibited a specific BIA vector distribution compared to the reference population and were slightly more hydrated than female athletes. BIVA validation may be an essential step to allow its use among university students to assess dehydration in a non-invasive, practical, and inexpensive way.

A Passive Perspiration Inspired Wearable Platform for Continuous Glucose Monitoring.

The demand for glucose monitoring devices has witnessed continuous growth from the rising diabetic population. The traditional approach of blood glucose (BG) sensor strip testing generates only intermittent glucose readings. Interstitial fluid-based devices measure glucose dynamically, but their sensing approaches remain either minimally invasive or prone to skin irritation. Here, a sweat glucose monitoring system is presented, which completely operates under rest with no sweat stimulation and can generate real-time BG dynamics. Osmotically driven hydrogels, capillary action with paper microfluidics, and self-powered enzymatic biochemical sensor are used for simultaneous sweat extraction, transport, and glucose monitoring, respectively. The osmotic forces facilitate greater flux inflow and minimize sweat rate fluctuations compared to natural perspiration-based sampling. The epidermal platform is tested on fingertip and forearm under varying physiological conditions. Personalized calibration models are developed and validated to obtain real-time BG information from sweat. The estimated BG concentration showed a good correlation with measured BG concentration, with all values lying in the A+B region of consensus error grid (MARD = 10.56% (fingertip) and 13.17% (forearm)). Overall, the successful execution of such osmotically driven continuous BG monitoring system from passive sweat can be a useful addition to the next-generation continuous sweat glucose monitors.

Effects of hypobaric hypoxia on human physiological and psychological responses in hot-humid environments

The hot-humid and hypobaric hypoxic environment hampers human physiological and psychological responses. In this study, 10 healthy participants were recruited to walk on a treadmill at 4 km/h in a hypobaric chamber under nine experimental conditions involving three air temperatures (Ta = 33, 37, and 40 °C), and three barometric pressures (PB = 96.5, 65.7, and 63.2 kPa). At 33 and 37 °C, the mean skin temperature, oral temperature, and sweat rate were not significantly affected by hypobaric hypoxia. The diastolic blood pressure, systolic blood pressure, and oxygen saturation decreased significantly, while the heart rate increased significantly under hypobaric hypoxic conditions. At 40 °C, the heart rate and diastolic blood pressure were not significantly affected by hypobaric hypoxia, while the oral temperature was significantly higher at 63.2 kPa than at 65.7 and 95.6 kPa. The remaining physiological parameters exhibited similar patterns as those at 33 and 37 °C. In conclusion, higher Ta had the most substantial effects on the cardiovascular system. Additionally, individuals should not work in environments where the Ta exceeds the body core temperature, especially at higher altitudes, as the risk of heat-related injuries could increase. At various Ta, the thermal sensation and acceptability were not significantly affected by hypobaric hypoxia, while a decrease in PB to 63.2 kPa resulted in a significant increase in tolerance, along with a notable reduction in exposure time. Therefore, this study provides valuable information concerning the physiological and psychological responses of humans exposed to working conditions similar to those tested.

Efficacy of the FIFA cooling break heat policy during an intermittent treadmill football simulation in hot conditions in trained males

ObjectiveTo evaluate the efficacy of the Fédération Internationale de Football Association (FIFA) cooling break policy against alternative cooling configurations in attenuating thermal strain during simulated football in the heat.Methods12 males...

Cluster Analysis Identifies Clinical Phenotypes of Primary Hyperhidrosis

Introduction: Identifying subgroups of patients with primary hyperhidrosis (PHH) can improve the understanding of the disease pathophysiology. The study objective was to determine the naturally occurring subgroups of patients with PHH based on clinical characteristics. Methods: In this retrospective cohort study, data were collected from participants included in a clinical trial. The data were collected between January 2020 and June 2021 from outpatients with PHH attending a dermatologic department in Denmark. Overall, 84 patients with PHH were screened for inclusion in the clinical trial. Of these, 41 met the eligibility criteria. Four participants were excluded because of missing data. The main outcome was the identification of subgroups of patients with PHH using an unsupervised hierarchical cluster analysis. Results: Overall, 37 patients were included {28 (76.7%) females; median age at inclusion 28.0 (interquartile range [IQR] 24.0–38.3); median body mass index 24.9 (IQR 20.9–27.4); median age of onset 13.0 (IQR 9.5–18.5); and 26 (70.3%) had a familial disposition toward PHH}. Two clusters of 18 and 17 patients were identified. The first cluster had, when compared to the second, a younger age of onset (median age 11.0 [IQR 0–13.0] vs. 17.0 [IQR 15.0–21.0], p = 0.003) and higher sweat rates on gravimetry (median 175.0 [IQR 121.2–252.5] vs. 40.0 [IQR 20.0–60.0] milligrams of sweat/5 min, p < 0.001) and transepidermal water loss (median 93.7 [IQR 91.2–97.8] vs. 59.0 [IQR 44.4–73.2] g/m2/h, p < 0.001). No differences were observed for the other variables. Conclusions: This study identifies 2 subgroups of patients with PHH. The patients with an onset of PHH during childhood had a substantially higher sweat and evaporation rate in adulthood than those with an onset during adolescence. These findings may imply a changed understanding of the pathophysiology of PHH, by indicating that an early disease onset can lead to a worse disease course.

Heat strain differences walking in hot-dry and warm-wet environments of equivalent wet bulb globe temperature

ABSTRACT Wet bulb globe temperature (WBGT) is a commonly used measure to predict heat strain in workers. Different combinations of environmental conditions can create equivalent WBGT, yet it remains unknown whether biophysical, physiological, and perceptual responses vary when working in different but equivalent hot conditions. The purpose of the study was to compare body heat storage and physiological and perceptual strain during walking in hot-dry and warm-wet conditions of the same WBGT. Twelve subjects (age: 22 ± 2 y) walked for 90 min at 60% maximum heart rate in a 27.8°C WBGT environment of hot-dry (HD: 40°C, 19% relative humidity) or warm-wet (WW: 30°C, 77% relative humidity) conditions. Partitional calorimetry was used to estimate heat storage. Core temperature at 90 min (HD: 38.5 ± 0.5°C; WW: 38.4 ± 0.3°C, p = 0.244) and cumulative heat storage (HD: 115 ± 531 Kj; WW: 333 ± 269 Kj, p = 0.242) were not different. At 90 min, heart rate was not different (HD: 160 ± 19 bpm; WW: 154 ± 15 bpm, p = 0.149) but skin temperature (HD: 36.6 ± 0.9°C; WW: 34.7 ± 0.6°C, p < 0.001), thirst (HD: 6.8 a.u.; WW: 5.3 a.u. p = 0.043), and sweat rate (HD: 15.1 ± 4.4 g·min−1; WW: 10.0 ± 4.1 g·min−1, p < 0.001) were greater in HD compared to WW. Hot environments of equivalent 27.8°C WBGT created equivalent core temperature despite differences in physiological strain during exercise, including earlier onset of cardiovascular strain, greater sweat rate, and higher skin temperature compared to a WW environment. ClinicalTrials.gov ID NCT04624919.

(Invited) Wearable Flexible Microfluidic Biosensor for Sweat Monitoring

As we enter the post-pandemic era, our lives have certainly become more convenient than before, due to the advancement and elimination of technologies that became practical or widespread during the pandemic. Among these, technologies related to non-invasive bioinstrumentation, which can be used at an individual level to access one's own health information, have become increasingly important. Non-invasive bioinstrumentation can be broadly divided into the measurement of physical information (shape, activity and so on) and the measurement of chemical information, i.e. the components of the body. For example, facial shape is widely used for personal identification, while weight and energy expenditure related to activity are easily managed by smartphones. In contrast, chemical sensing, which is often difficult to sample and requires a wet environment for measurement, still requires breakthroughs to be used by individuals with the same ease as physical sensing.In the research field of non-invasive biomedical measurements, the technology is often developed in the form of wearable systems. Wearable microfluidic devices have been intensively studied for the measurement of body components. We focused on sweat, which contains a variety of biomarkers, and have developed a wearable microfluidic biosensing system that measures sweat components in real-time. Sweat is secreted from sweat glands on the skin of the entire body, making it easily accessible and less mentally demanding to collect. On the other hand, there are problems with sampling methods for reliable measurement, such as large fluctuations in the sweat rate and evaporation from the skin surface during secretion. We overcame this problem by using a wearable microfluidic device to transport the full amount of sweat from the sweat gland to a downstream biosensor by carrier flow, and developed a wristwatch biosensing system to monitor the constituents released as sweat independent of sweat rate.The wristwatch sweat sensor consists of a PDMS sweat sampling device, a biosensor, a fluid controller and a wireless control circuit with Bluetooth Low Energy and external analogue I/O. Communication with the mobile device is via Bluetooth Low Energy. Our method has the advantage that secretions are transported by dissolution in the carrier stream and can therefore be reliably monitored even at very low sweat levels. The pump is controlled by an microcontroller unit, so the flow rate can be controlled in real time according to the sweat rate and target substances, and the sensitivity can be improved at the expense of temporal resolution by running the pump intermittently, i.e. allowing secretions to accumulate in the carrier flow for a certain time before measurement.We monitored changes in sweat lactic acid in response to exercise load using an ergometer. The results showed an increase in sweat lactate with increasing exercise intensity, with a dependence on sweat rate. By measuring sweat at rest, we found that the lactate accumulated in the sweat glands and on the skin's surface were dissolved by the biosensor in the early stages of measurement, while the signals from the sweat glands became dominant after these had been sufficiently decreased. These results suggest that our system appropriately reflects the physiological phenomena associated with sweating. The presentation will also include the behaviour of lactic acid in sweat, which was detected by our system for the first time.