Metabolic Effects of Isoenergetic High-Intensity Interval Training and Moderate-Intensity Continuous Training in Adults with Type I Diabetes

Type 1 diabetes (T1D) is characterized by insulin deficiency and impaired glucose homeostasis. Exercise is recommended for individuals with T1D, with moderate-intensity continuous training (MICT) favored due to concerns of hypoglycemia with high-intensity interval training (HIIT). PURPOSE: The extent to which these exercise strategies alter metabolomic signatures of macronutrient metabolism in T1D is unknown. The current study evaluated glycemic variability and metabolomic responses around energy-matched HIIT and MICT in individuals with T1D. METHODS: Fourteen adults with T1D (7 females, 7 males) completed three conditions in a randomized crossover design: HIIT (10 1-minute intervals at 90% VO 2 peak), MICT (15-20 min steady-state cycling at 65% VO 2 peak), and no exercise (control, CON). Twenty-four-hour glycemic responses via continuous glucose monitor and metabolomics assessed by blood samples before, after, and 1 h after exercise by targeted mass spectrometry and nontargeted gas chromatography-mass spectrometry. RESULTS: Average whole-day glucose levels were higher on the day of HIIT (167.48 ± 66.96 mg/dL; group × time P = 0.021) and MICT (166.46 ± 61.35 mg/dL; group × time P = 0.039) compared with CON (150.43 ± 61.69 mg/dL) with no difference between HIIT and MICT (group × time P = 0.999). Area under the curve for glucose was not different between HIIT, MICT, and CON on the day of exercise (group × time P = 0.961). After MICT, long-chain acylcarnitine C14:2 (0.06 ± 0.04 µmol/L) was higher than after HIIT (0.04 ± 0.02 µmol/L; group × time P = 0.008), with C16:1 (group × time P = 0.046) and C16:2 (group × time P = 0.021) higher than CON. CONCLUSIONS: In adults with T1D, HIIT and MICT elevated average glucose on the day of exercise, with greater fatty acid oxidation after MICT. These data support the metabolic safety and distinct fuel utilization of both exercise modalities in T1D.