Older Adults with Type 2 Diabetes Store More Heat during Exercise
ABSTRACT
It is unknown if diabetes-related reductions in local skin blood flow (SkBF) and sweating (LSR) measured during passive heat stress translate into greater heat storage during exercise in the heat in individuals with type 2 diabetes (T2D) compared to non-diabetic control (CON) subjects.
Purpose:
To examine the effects of T2D on whole-body heat exchange during exercise in the heat.
Methods:
Ten (6 males and 4 females) adults with T2D and 10 adults (6 males and 4 females) without diabetes matched for age, sex, body surface area, and fitness cycled continuously for 60 min at a fixed rate of metabolic heat production (~370 W) in a whole-body direct calorimeter (30[degrees]C and 20% RH). Upper back LSR, forearm SkBF and rectal temperature (Tre) and heart rate were measured continuously. Whole-body heat loss and changes in body heat content ([DELTA]Hb) were determined using simultaneous direct whole-body and indirect calorimetry.
Results:
Whole-body heat loss was significantly attenuated from 15 min throughout the remaining exercise with the differences becoming more pronounced over time for T2D relative to CON (p=0.004). This resulted in a significantly greater [DELTA]Hb in T2D (360+/-33; CON: 265+/-28 kJ, p=0.013). No differences were measured during recovery (T2D: -87+/-22; CON: -132+/-21 kJ, p=0.076). By the end of the 60-min recovery, the T2D group lost only 21% (79 kJ) of the total heat gained during exercise whereas their non-diabetic counterparts lost in excess of 55% (131 kJ). No differences were observed in LSR (p=0.361), SkBF (p=0.528), Tre (p=0.388) or heart rate (p=0.179) during exercise or recovery.
Conclusion:
Older adults with T2D have a reduced capacity to dissipate heat during exercise resulting a greater heat storage and therefore level of thermal strain.
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