Tattoos do not affect exercise-induced localised sweat rate or sodium concentration

Abstract

ObjectivesSkin tattoos have been shown to reduce localised sweat rate and increase sweat sodium concentration ([Na+]) when sweating is artificially stimulated. This study investigated whether similar responses are observed with exercise-induced sweating. DesignUnblinded, within-participant control, single trial. MethodsTwenty-two healthy individuals (25.1±4.8 y (Mean±SD), 14 males) with a unilateral tattoo ≥11.4cm2 in size, ≥2 months in age, and shaded ≥50% participated in this investigation. Participants undertook 20min of intermittent cycling (4×5min intervals) on a stationary ergometer in a controlled environment (24.6±1.1°C; 64±6% RH). 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 used to determine differences between contralateral sites. ResultsTattoo vs. Non-Tattoo: Neither sweat rate (Mean±SD: 0.92±0.37 vs. 0.94±0.43mg·cm−2·min−1, respectively; p=0.693) nor sweat [Na+] (Median(IQR): 37(32–52) 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±0.53mg·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 sweat rate and [Na+] between Tattoo vs. Non-Tattoo were inside the range of the within participant variability (sweat rate CVi=5.4%; sweat [Na+] CVi=4.4%). ConclusionsSkin tattoos do not appear to alter the rate or [Na+] of exercise-induced sweating. The influence of skin tattoos on localised sweat responses may have previously been over-estimated.