High-intensity interval training improves insulin sensitivity in individuals with prediabetes

Objective: To examine the separate and combined effects of low-volume high-intensity interval training (HIIT) and walking compared with no training on insulin sensitivity and skeletal metabolic capacity in individuals with prediabetes. Design: Individuals were randomized to: (1) control (no exercise), (2) HIIT (3 × 20 s's cycle sprint 3 times weekly), (3) HIIT + walking (walking >10 000 steps/day), or (4) walking for 12 weeks. Methods: Insulin sensitivity was assessed by an oral glucose tolerance test at baseline and end-of-trial. Additionally, proteins important for mitochondria capacity and insulin sensitivity were measured in the vastus lateralis muscle. Results: Seventy sedentary individuals with prediabetes (women n = 36; age: 60.8 ± 11.3 years (mean ± SD); body mass index: 31.6 ± 4.4 kg/m2; fasting plasma glucose: 6.6 ± 0.8 mmol/L; glycated hemoglobin A1c 5.7 ± 0.4% (39.0 ± 4.3 mmol/mol) were included. Compared with control, peripheral insulin sensitivity (measured by the Cederholm index) was significantly improved with HIIT (estimated treatment difference [ETD]: 18.5% [95% confidence interval (CI): 7.4; 28.3%] and HIIT + walking [ETD: 15.7% (95% CI: 4.4; 25.6%)]), but not with walking alone (ETD: 9.4% [95% CI: −2.5; 19.9%]). Whole-body insulin sensitivity (measured by the Matsuda index) was significantly increased with HIIT + walking (ETD: 28.0% [95% CI: 10.3; 42.3%]) and walking alone (ETD: 42.3% [95% CI: 28.3; 53.5%]), but not with HIIT alone (ETD: 17.0% [95% CI: −4.0; 33.7%]). Protein expression of proteins involved in mitochondrial capacity in skeletal muscle and glucose uptake were most improved with HIIT + walking, and no significant effects were observed with walking alone. Conclusions: Twelve weeks of low-volume HIIT training can improve glucose control and induces adaptations in skeletal muscle important for metabolic health in individuals with prediabetes.