Agreement between the ventilated capsule and the KuduSmart(R) device for measuring sweating responses to passive heat stress and exercise

The present study assessed agreement between the KuduSmart(R) device and the ventilated capsule (VC) technique for measuring: i) minute-averaged local sweat rate (LSR); ii) sweating onset; iii) thermosensitivity; and iv) steady-state LSR, during passive heat stress and exercise. On two separate occasions for each heat stress intervention, participants were either passively heated by recirculating hot water (49{degrees}C) through a tube-lined garment until rectal temperature increased 1{degrees}C over baseline (n=8), or walked on a treadmill for 60 minutes at a fixed rate of heat production (n=9). LSR of the forearm was concurrently measured with a VC and the KuduSmart(R) device secured within [~]2 cm. Mean body temperature was calculated as the weighted average between rectal (80%) and mean skin (20%) temperature. Using a ratio scale Bland-Altman analysis with the VC as the reference, the KuduSmart(R) device demonstrated systematic bias for minute-averaged LSR (1.19 [1.09, 1.28]) and steady-state LSR (1.16 [1.09,1.23]), however no bias for thermosensitivity (1.08 [1.00, 1.16]) or sweating onset (1.00 [1.00, 1.00]). Although poor agreement was observed for minute-averaged LSR (CV = 43.3%), more than 73% of all observations with the KuduSmart(R) device (n=2795) were within an absolute error of < 0.2 mg/cm2/min to the VC. The KuduSmart(R) device demonstrated acceptable agreement for steady-state LSR (CV = 19.5%) and thermosensitivity (CV = 21.7%), and almost perfect agreement for sweating onset (CV = 0.14%). Collectively, the KuduSmart(R) device may be a satisfactory in-field solution for assessing the sweating response to heat stress.