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

PURPOSE: 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 post-exercise postural sway in cool and warm-humid environments. METHODS: Middle-aged men with (n=15, age: 58±5 years, V̇O2peak: 31±6 ml/kg/min) and without T2D (CON) (n=15, age: 58±4 years, V̇O2peak: 34±6 ml/kg/min) walked for an hour at 6.0 W/kg in 22 °C, 50%RH (COOL) and 32 °C, 70%RH (WARM) in a randomised counterbalanced crossover design. Gastrointestinal temperature (Tgi), skin temperatures (Tsk), heart rate (HR) and whole body sweat rate (WBSR) were assessed in this study. Postural balance (i.e., centre of pressure (COP) excursions), handgrip strength and five-time sit-to-stand performance were assessed pre- and post-exercise. RESULTS: Men with T2D showed greater increase in postural instability, particularly when balancing on an unstable surface after WARM compared to COOL, despite similar post-exercise Tgi, Tsk, HR, and WBSR between groups. Anteroposterior COP (WARM>COOL: +9mm [95% CI: 3 to 15mm], d = 0.86, P = 0.037); total COP excursion (WARM>COOL: +126mm [95% CI: 48 to 204mm], d =0.87, P = 0.018), and COP mean velocity (WARM>COOL: +5mm/s [95% CI: 2 to 7mm/s], d = 1.49, P = 0.003) were increased only in men with T2D in WARM. CONCLUSIONS: 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.