Exercise intensity- and body region-specific differences in sweating in middle-aged-to-older men with and without type 2 diabetes

Type 2 diabetes is associated with reduced whole-body sweating during exercise-heat stress. However, it is unclear if this impairment is related to exercise intensity and whether it occurs uniformly across body regions. We evaluated whole-body (direct calorimetry) and local (ventilated-capsule technique; chest, back, forearm, thigh) sweat rates in physically active men with type 2 diabetes (T2D; aged 59 (7) years; V̇O_2peak 32.3 (7.6) mL·kg^-1·min^-1; n=26; HbA_1c 5.1-9.1%) and without diabetes (Control; aged 61 (5) years; V̇O_2peak 37.5 (5.4) mL·kg^-1·min^-1; n=26) during light (~40%V̇O_2peak), moderate (~50%V̇O_2peak), and vigorous (~65%V̇O_2peak) intensity exercise (elicited by fixing metabolic heat production at ~150, 200, 250 W·m^-2, respectively) in 40°C, ~17% relative humidity. Whole-body sweating was ~11% (T2D-Control mean difference [95% confidence interval]: -37 [-63, -12] g·m^-2·h^-1) and ~13% (-50 [-76, -25] g·m^-2·h^-1) lower in the T2D compared to the Control group during moderate- and vigorous- (p≤0.001), but not light-intensity exercise (-21 [-47, 4] g·m^-2·h^-1; p=0.128). Consequently, the diabetes-related reductions in whole-body sweat rate were 2.3 [1.6, 3.1] times greater during vigorous relative to light exercise (p<0.001). Further, these diabetes-related impairments in local sweating were region-specific during vigorous-intensity exercise (group × region interaction: p=0.024), such that the diabetes-related reduction in local sweat rate at the trunk (chest, back) was 2.4 [1.2, 3.7] times greater than that at the limbs (thigh, arm). In summary, when assessed under hot, dry conditions, diabetes-related impairments in sweating are exercise intensity-dependent and greater at the trunk compared to the limbs.