Multiple regression analyses to determine the effect of sweating rate and tattoo characteristics on sweat outcome...

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.

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.

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.

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.

NCT04240951 was registered on January 27, 2020 and NCT04920266 was registered on June 9, 2021.