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

Type 2 diabetes (T2D) 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) yr; 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) yr; 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 with 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). Furthermore, 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 with the limbs.NEW & NOTEWORTHY This study evaluates the influence of exercise intensity on decrements in whole body sweating associated with type 2 diabetes. Furthermore, it investigates whether diabetes-related sweating impairments were exhibited uniformly or heterogeneously across body regions. We found that whole body sweating was attenuated in the type 2 diabetes group relative to control participants during moderate- and vigorous-intensity exercise but not light-intensity exercise; impairments were largely mediated by reduced sweating at the trunk rather than the limbs.