Postural Instability Is Greater in Men with Type 2 Diabetes after Exertional Heat Stress

Individuals with type 2 diabetes (T2D) face a greater risk of heat-related illness during exercise compared to healthy counterparts. Here, we examined how T2D affects thermoregulation and postexercise postural sway in cool and warm-humid environments.

Middle-aged men with ( n = 15, age: 58 ± 5 yr, : 31 ± 6 mL · kg -1 · min -1 ) and without T2D (CON) ( n = 15, age: 58 ± 4 yr, : 34 ± 6 mL · kg -1 · min -1 ) walked for an hour at 6.0 W · kg -1 in 22°C, 50%RH (COOL) and 32°C, 70%RH (WARM) in a randomized counterbalanced crossover design. Gastrointestinal temperature (T gi ), skin temperatures (T sk ), heart rate, and whole-body sweat rate were assessed in this study. Postural balance (i.e., center of pressure [COP] excursions), handgrip strength and five-time sit-to-stand performance were assessed pre- and postexercise.

Men with T2D showed greater increase in postural instability, particularly when balancing on an unstable surface after WARM compared to COOL, despite similar postexercise T gi , T sk , HR, and whole-body sweat rate between groups. Anteroposterior COP (WARM > COOL: +9 mm [95% CI: 3-15 mm], d = 0.86, P = 0.037); total COP excursion (WARM > COOL: +126 mm [95% CI: 48-204 mm], d = 0.87, P = 0.018), and COP mean velocity (WARM > COOL: +5 mm · s -1 [95% CI: 2-7 mm · s -1 ], d = 1.49, P = 0.003) were increased only in men with T2D in WARM.

Postural instability increased only in middle-aged men with T2D in humid heat, despite comparable thermoregulatory responses with age-matched men without T2D. This may be attributed to T2D-associated impairments (e.g., altered hemodynamics and/or vibrotactile sensitivity) which can lead to an increased fall risk during or after exercise in the heat.