Validation of a novel method to quantify local axilla sweating, SweatSENSE

The aim of this study was to validate the ability of the novel SweatSENSE technique to measure local axilla sweating. The local axilla sweating responses to a range of physical activities were measured in 30 healthy females (28 ± 5 yr, 163 ± 7 cm; 62 ± 9 kg). Participants completed low-to moderate-intensity treadmill walking, stepping, and cycling in a 3-h protocol. Left axilla sweating was intermittently recorded using the novel SweatSENSE method, in which non-hydrochromic sweat-responsive paper sensors with PCDA polymer were placed in the axilla vault for 5 s. The sensors were analysed for the proportional colour change as an index of instantaneous local sweating. Percentage total sweat coverage (%TC) of the patches was determined. Ipsilateral axilla sweating was continuously recorded using capacitance hygrometry (CH). Intraclass correlation coefficient (ICC) analyses was used to examine the agreement between the CH and SweatSENSE %TC data for each participant. Heart rate, core and skin temperatures, ratings of perceived exertion (RPE) and thermal discomfort were also recorded. Heart rate (100 ± 25 beats.min⁻¹, P < 0.05) and T_core increased during the protocol (37.82 ± 0.23 °C, P < 0.05). Thermal discomfort increased from ‘neutral’ to ‘warm’ and RPE increased to ‘somewhat hard’ during the protocol (both P < 0.05). Local axilla sweating (CH and the SweatSENSE method) increased during each physical activity bout and progressively throughout the protocol (both P < 0.05). Twenty one out of thirty participants demonstrated significant ICC between axilla SweatSENSE and capacitance hygrometry sweating data [average (95 % confidence intervals] ICC; 0.483 (0.191–0.713)) indicating a moderate agreement between SweatSENSE and capacitance hygrometry, suggesting a moderate level of validity of the SweatSENSE method.