Purpose To compare local sweating rate (LSR) and local sweat sodium ([Na+]), chloride ([Cl−]), and potassium ([K+]) concentrations of tattooed skin and contralateral non-tattooed skin during exercise. Methods Thirty-three recreational exercisers (17 men, 16 women) with ≥ 1 unilateral permanent tattoo on the torso/arms were tested during cycling, running, or fitness sessions (26 ± 4 °C and 54 ± 13% relative humidity). Forty-eight tattoos with a range of ink colors, ages (3 weeks to 20 years), and densities (10–100%) were included. Before exercise, the skin was cleaned with alcohol and patches (3 M Tegaderm + Pad) were placed on the tattooed and contralateral non-tattooed skin. LSR was calculated from sweat mass (0.80 ± 0.31 g), patch surface area (11.9 cm2), and duration (62 ± 14 min). Sweat [Na+], [Cl−], and [K+] were measured via ion chromatography. Results Based on the analysis of variance results, there were no differences between tattooed and non-tattooed skin for LSR (1.16 ± 0.52 vs. 1.12 ± 0.53 mg/cm2/min; p = 0.51), sweat [Na+] (60.2 ± 23.5 vs. 58.5 ± 22.7 mmol/L; p = 0.27), sweat [Cl−] (52.1 ± 22.4 vs. 50.6 ± 22.0 mmol/L; p = 0.31), or sweat [K+] (5.8 ± 1.6 vs. 5.9 ± 1.4 mmol/L; p = 0.31). Multiple regression analyses suggested that younger tattoos were associated with higher sweat [Na+] (p = 0.045) and colorful tattoos were associated with higher sweat [Cl−] (p = 0.04) compared with contralateral non-tattooed skin. Otherwise, there were no effects of LSR or tattoo characteristics on regression models for LSR or sweat electrolyte concentrations. Conclusion There were no effects of tattoos on LSR and sweat [K+] during exercise-induced sweating, but tattoo age and color had small effects on sweat [Na+] and sweat [Cl−], respectively. Clinical trial identifiers NCT04240951 was registered on January 27, 2020 and NCT04920266 was registered on June 9, 2021.

Permanent tattooing is common on areas of the skin typically sampled for sweat diagnostics, yet its potential to alter local sweat concentration and excretion rate (ER) of metabolites and other compounds is unknown. The purpose of this study was to investigate the influence of tattooed skin (TAT) on local sweat concentration and ER of urea nitrogen (UN), cortisol (CORT), glucose (GLU) and lactate (LAC) when compared to contralateral non‐tattooed skin (NT) during a group fitness exercise session. Moderately trained participants (males n=8, females n=8, 34±8 y) with at least one permanent tattoo (age of tattoo 7±5 y) on the upper body (arm, scapula, or thorax regions) underwent a ~60 minute outdoor (~27±3°C, 63±4% RH, 26±3°C WBGT) group fitness exercise session. Sweat was collected with absorbent patches (3MTMTegaderm+PAD) placed on the TAT and on NT. Patches were monitored during exercise and removed upon moderate saturation. Local sweat rate (LSR) was calculated from sweat mass over patch surface area (11.9 cm2) and exercise duration (56±2 min). Excretion rates (ER) were calculated as the product of analyte concentration and local SR. Sweat was analyzed by ELISA for UN (Invitrogen, ThermoFisher Scientific), CORT (Invitrogen, ThermoFisher Scientific), GLU (Caymen Chemical Co.) and LAC (LSBio). To evaluate differences between TAT and NT skin, paired t‐tests or Wilcoxon signed rank tests were used. Significance level was set at p<0.05. Data are presented as mean±SD or median±IQR for normally and non‐normally distributed data respectively. There were no differences in LSR for TAT vs. NT conditions (1.1±0.7 vs 1.2±0.6 mg/cm2/min; p=0.93). TAT and NT skin had similar concentrations for UN (19.2±6.0 vs 20.7±6.1 mg/dL; p=0.28), CORT (2.4±1.3 vs 2.5±1.4 ng/mL; p=0.41), GLU (0.22±0.3 vs 0.24±0.2 mg/dL; p=0.31), and LAC (5.8±6.3 vs 5.9±6.6 mM; p=0.83). ERs were also similar for all analytes: UN (252±150 vs 270±136 ng/cm2/min; p=0.34), CORT (1.8±3.4 vs 2.1±3.4 pg/cm2/min; p=0.46), GLU (2.3±1.6 vs 2.3±2.4 ng/cm2/min; p=0.40) and LAC (6.4±10.9 vs 7.1±10.1 ng/cm2/min; p>0.999). In conclusion, TAT does not appear to affect the LSR, concentration, or ER of select analytes during ~60 min of fitness exercise.

The purpose of this study was to compare a wearable microfluidic device and standard absorbent patch in measuring local sweating rate (LSR) and sweat chloride concentration ([Cl−]) in elite basketball players. Participants were 53 male basketball players (25 ± 3 years, 92.2 ± 10.4 kg) in the National Basketball Association’s development league. Players were tested during a moderate-intensity, coach-led practice (98 ± 30 min, 21.0 ± 1.2 °C). From the right ventral forearm, sweat was collected using an absorbent patch (3M Tegaderm™ + Pad). Subsequently, LSR and local sweat [Cl−] were determined via gravimetry and ion chromatography. From the left ventral forearm, LSR and local sweat [Cl−] were measured using a wearable microfluidic device and associated smartphone application-based algorithms. Whole-body sweating rate (WBSR) was determined from pre- to postexercise change in body mass corrected for fluid/food intake (ad libitum), urine loss, and estimated respiratory water and metabolic mass loss. The WBSR values predicted by the algorithms in the smartphone application were also recorded. There were no differences between the absorbent patch and microfluidic patch for LSR (1.25 ± 0.91 mg·cm−2·min−1 vs. 1.14 ±0.78 mg·cm−2·min−1, p = .34) or local sweat [Cl−] (30.6 ± 17.3 mmol/L vs. 29.6 ± 19.4 mmol/L, p = .55). There was no difference between measured and predicted WBSR (0.97 ± 0.41 L/hr vs. 0.89 ± 0.35 L/hr, p = .22; 95% limits of agreement = 0.61 L/hr). The wearable microfluidic device provides similar LSR, local sweat [Cl−], and WBSR results compared with standard field-based methods in elite male basketball players during moderate-intensity practices.

There is interest in the potential of sweat cytokines to serve as non‐invasive biomarkers to monitor immune system function, but many practical questions remain. For example, sweat constituents collected from tattooed (TAT) skin regions may differ from skin regions without permanent tattooing. The purpose of this investigation was to determine if tattooed skin (TAT) differed from contralateral non‐tattooed skin (NT) for sweat cytokines including: EGF, IL‐10, IL‐1α, IL‐1β, IL‐6, IL‐8, TNF‐α, and IL‐31 concentrations and excretion rates during a group fitness exercise session. Moderately trained individuals (males n=8, females n=8, 34±8 y) with at least one permanent tattoo on the upper body (wrist, forearm, tricep, bicep, scapula, shoulder, or torso) participated in a ~60 minute outdoor (~27±3°C, 63±4% RH) group fitness exercise session. Absorbent patches (3M Tegaderm™ + Pad) were used to collect sweat on both TAT and NT skin. Patches were monitored during the exercise session and removed upon moderate saturation. Sweat cytokine concentrations were measured using Multiplex (EMD Millipore, MagPix) customized kits. Local sweat rate (LSR) was calculated from sweat mass over patch surface area (11.9 cm2) and duration of exercise (56±2 min). Excretion rates were calculated as the product of LSR and cytokine concentration. To evaluate differences between TAT and NT skin, paired t‐tests or Wilcoxon signed rank tests were used. Significance level was set at p<0.05. Data are presented as mean±SD for normally and non‐normally distributed data. There were no differences in LSR for TAT vs. NT skin regions (1.20±0.62 vs 1.24±0.53 mg/cm2/min; p=0.70). There were no differences between TAT and NT skin for concentrations of EGF (45±29 vs 53±31 pg/mL; p=0.10), IL‐10 (0.03±0.04 vs 0.07±0.13 pg/mL; p=0.21), IL‐1β (1.66±1.12 vs 1.86±1.07 pg/mL; p=0.55), IL‐8 (0.60±0.50 vs 0.56±0.64 pg/mL; p=0.27), IL‐1α (618±550 vs 807±913 pg/mL; p=0.3) or TNF‐α (0.40±0.05 vs 0.40±0.04 pg/mL; p=0.85). There was below minimum or no level of detection for TAT and NT skin for IL‐6 and IL‐31. Excretion rates were significantly different between TAT and NT skin for EGF (0.05±0.04 vs 0.06±0.03 pg/cm2/min; p=0.04). In summary, EGF excretion rate was lower in TAT skin than NT skin during exercise, but TAT did not affect the concentrations or excretion rates of any other cytokines measured.