Sweat Rate Research Articles

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.

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

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

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

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

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.

(Keynote) Soft Microfluidic Analysis Systems for the Skin

Recent advances in materials science, chemical engineering and mechanics design establish the foundations for high performance classes of microfluidic lab-on-a-chip technologies that have physical properties matched those of the human skin. The resulting devices can integrate with the surface of the skin in a water-tight yet physically imperceptible fashion, to provide real-time measurements of sweat rate and total sweat loss, along with continuous, clinical-quality biochemical information on physiological status using a combination of colorimetric and electrochemical techniques. This talk summarizes the key ideas and presents application examples in sports performance, worker safety, medical diagnostics and nutritional monitoring.

Time-course for onset and decay of physiological adaptations in endurance trained athletes undertaking prolonged heat acclimation training

ABSTRACT Short-term heat acclimation (HA) appears adequate for maximizing sudomotor adaptations and enhancing thermal resilience in trained athletes. However, for enhanced erythropoiesis and transfer effects to exercise capacity in cooler environments, prolonged HA appears necessary. To establish the time-course for physiological adaptations and performance effects, 20 male elite cyclists were divided into an intervention group (HEAT; n = 10) completing 5 weeks of HA (six one-hour HA-training sessions per week) and control (n = 10) tested pre and post in hot (40°C) and cool conditions (20°C). HEAT completed tests at 40°C every week during HA with measures of sweat rate and [Na+] and a decay test 2 weeks after termination of HA. HEAT improved time for exhaustion by 15 min (p < 0.001) in the 40°C test, increased sweat rate by 0.44 L/hour (p < 0.001), and lowered sweat sodium concentration [Na+] by 14.1 mmol/L (p = 0.006) from pre- to post-HA, with performance returning to pre-HA levels in the 2-week decay test. Total hemoglobin mass (tHbmass) was increased by 30 grams (+3%, p = 0.048) after 3 weeks and 40 grams (+4%, p = 0.038) after 5 weeks in HEAT but returned to pre-HA levels at the 2-week decay test. HEAT improved incremental peak power output (+12 W, p = 0.001) without significant changes in maximal oxygen uptake (p = 0.094). In conclusion, improvements in heat exercise tolerance and sudomotor adaptations materialized during the first ~3 weeks and the entire 5 weeks of HA augmented both cool exercise capacity and tHbmass. However, the 2-week post-HA evaluation demonstrated a rapid decay of physiological adaptations and exercise capacity in the heat.

The effect of female breast surface area on heat-activated sweat gland density and output.

Female development includes significant morphological changes across the breast. Yet, whether differences in breast surface area (BrSA) modify sweat gland density and output remains unclear. The present study investigated the relationship between BrSA and sweat gland density and output in 22 young to middle-aged women (28 10years) of varying breast sizes (BrSA range: 147-561cm2) during a submaximal run in a warm environment (32 0.6°C; 53 1.7% relative humidity). Local sweat gland density and local sweat rate (LSR) above and below the nipple and at the bra triangle were measured. Expired gases were monitored for the estimation of evaporative requirements for heat balance (Ereq, in W/m2). Associations between BrSA and (i) sweat gland density; (ii) LSR; and (iii) sweat output per gland for the breast sites were determined via correlation and regression analyses. Our results indicated that breast sweat gland density decreased linearly as BrSA increased (r=-0.76, P<0.001), whereas sweat output per gland remained constant irrespective of BrSA (r=0.29, P=0.28). This resulted in LSR decreasing linearly as BrSA increased (r=-0.62, P=0.01). Compared to the bra triangle, the breast had a 64% lower sweat gland density (P<0.001), 83% lower LSR (P<0.001) and 53% lower output per gland (P<0.001). BrSA (R2=0.33, P=0.015) explained a greater proportion of variance in LSR than Ereq (in W/m2) (R2=0.07, P=0.538). These novel findings extend the known relationship between body morphology and sweat gland density and LSR, to the female breast. This knowledge could innovate user-centred design of sports bras by accommodating breast size-specific needs for sweat management, skin wetness perception and comfort.