Skin Tattoos Do Not Affect Exercise-induced Sweat Rate Or Sodium Concentration.

Abstract

PURPOSE: Skin tattoos have been shown to reduce sweat rate and increase sweat sodium concentration when sweating is artificially stimulated. This study investigated whether similar responses are observed with exercise-induced sweating. METHODS: Twenty-two healthy individuals (25.1±4.8 y (Mean±SD), 14 males) with a unilateral tattoo ≥11.4 cm2 in size, >2 months in age, and shaded ≥50% participated in this investigation. Participants undertook 20 min of intermittent cycling (4 x 5 min intervals) on a stationary ergometer in a controlled environment (24.6±1.1°C, RH 64±6%). Resultant sweat was collected into absorbent patches applied at two pairs of contralateral skin sites (pair 1: Tattoo vs. Non-Tattoo; pair 2: Control 1 vs. Control 2 (both non-tattooed)), for determination of sweat rate and sweat [Na+]. Paired samples t tests were employed to determine differences between contralateral sites. RESULTS:Tattoo vs. Non-Tattoo: Neither sweat rate (Mean±SD: 0.92±0.37 vs. 0.94±0.43 mg.cm-2.min-1, respectively; p=1.000) nor sweat [Na+] (Median(IQR): 36(32-53) vs. 37(31-45) mM.L-1, respectively; p=0.827) differed. Control 1 vs. Control 2: Neither sweat rate (Mean±SD: 1.19±0.53 vs. 1.19±0.53 mg.cm-2.min-1, respectively; p=0.917) nor sweat [Na+] (Median(IQR): 29(26-41) vs. 31(25-43) mM.L-1, respectively; p=0.147) differed. The non-significant differences for Tattoo vs. Non-Tattoo were within the range of normal variability (sweat rate CV=5.4%; sweat [Na+] CV=4.4%). CONCLUSIONS: Skin tattoos do not appear to alter rate or [Na+] of exercise-induced sweat. The influence of skin tattoos on thermoregulatory responses to exercise may have been over-estimated.