Optimal Insulin Correction Factor in Post-High-Intensity Exercise Hyperglycemia in Adults With Type 1 Diabetes: The FIT Study

Postexercise hyperglycemia, following high-intensity interval training (HIIT) in patients with type 1 diabetes (T1D), is largely underrecognized by the clinical community and generally undertreated. The aim of this study was to compare four multipliers of an individual's insulin correction factor (ICF) to treat post-HIIT hyperglycemia. The FIT study had a randomized, crossover design in physically active subjects with T1D (mean ± SD age 34.9 ± 10.1 years, BMI 25.5 ± 2.5 kg/m , and HbA 7.2 ± 0.9%) using multiple daily injections. Following an 8-week optimization period, with 300 units/mL insulin glargine used as the basal insulin, subjects performed four weekly sessions of 25 min of HIIT. If hyperglycemia (>8.0 mmol/L) resulted, subjects received a bolus insulin correction 15 min post-HIIT, based on their own ICF, adjusted by one of four multipliers: 0, 50, 100, or 150%. Seventeen subjects completed 71 exercise trials, of which 64 (90%) resulted in hyperglycemia. At 40 min postexercise, plasma glucose (PG) increased from mean ± SD 8.8 ± 1.0 mmol/L at baseline to 12.7 ± 2.4 mmol/L (increase of 3.8 ± 1.5 mmol/L). After correction, adjusted mean ± SE PG was significantly reduced for the 50% (-2.3 ± 0.8 mmol/L, < 0.01), 100% (-4.7 ± 0.8 mmol/L, < 0.001), and 150% (-5.3 ± 0.8 mmol/L, < 0.001) arms but had increased further in the 0% correction arm. Both the 100 and 150% corrections were more effective than the 50% correction ( < 0.01 and < 0.001, respectively) but were not different from each other. Hypoglycemia was rare. In post-HIIT hyperglycemia, correction based on a patient's usual ICF is safe and effective. Optimal PG reduction, with minimal hypoglycemia, occurred in the 100 and 150% correction arms.