Discussion | Relative to healthy counterparts, physically active middle-aged and older men with well-controlled type 2 diabetes had attenuated heat-loss capacity during exercise in the heat, due primarily to impaired sweat evaporation, which exacerbated thermal (body temperature) and cardiovascular (heart rate) strain. These preliminary findings indicate that exercise heat stress may pose a health concern in patients with type 2 diabetes, especially because physical activity is recommended for diabetes management. 5 However, participants with type 2 diabetes demonstrated a greater improvement in heatloss capacity than did healthy controls after heat acclimation. A randomized clinical trial of repeated brief, supervised exercise is warranted to determine whether heat acclimation during heat exposure offsets diabetes-related thermoregulatory impairments and health complications. Study limitations include the small sample size, the inclusion of only men and patients with well-controlled diabetes, and the specific exercise and environmental conditions.