Short-Acting Insulin Reduction Strategies for Continuous Cycle Ergometer Exercises in Patients with Type 1 Diabetes Mellitus

Background The fear of hypoglycemia is the strongest barrier when patients with type 1 diabetes mellitus consider physical activity. There is still a lack of information regarding pre- and post-exercise therapy adaptation strategies with respect to different exercise intensities corresponding to the three phases of lactate metabolism. Objectives The aim of this experimental, cross-sectional study was to investigate exercise intensity-dependent, short-acting insulin reductions to avoid hypoglycemia, applying standardized exercises using insulin degludec (®Tresiba/Novo Nordisk, Denmark). Methods Seven male participants with type 1 diabetes mellitus were switched to insulin degludec. Intensities for the 30 minutes continuous cycle ergometer exercise tests were set at 5% below (A) and above (B) the lactate turn point 1, and below (C) and above (D) the lactate turn point 2. Reductions in short-acting insulin were applied as following: by 25% for intensity A, by 50% for intensity B and by 75% for intensities C and D four hours before the start of exercise and immediately after exercise. Blood glucose, interstitial glucose, lactate, catecholamines, cortisol, IGF-1 and glucagon were measured. Results No hypoglycemic events occurred, but linear blood glucose decreases were observed: 2.01 ± 1.04 mmol.L^-1, P = 0.35 (A), 3.00 ± 1.54 mmol.L^-1, P = 0.48 (B), 3.42 ± 2.34 mmol.L^-1, P = 0.40 (C), and 3.70 ± 3.36 mmol.L^-1, P = 0.12 (D). Adrenaline, noradrenaline and IGF-1 (B, C, D, not A), dopamine (C, D, not A and B) and cortisol (A, C, D, not B) increased significantly from baseline, but not glucagon (P > 0.05). Interstitial glucose showed no post-exercise hypoglycemia. Conclusions The applied therapy adaptation before and after exercises was adequate to avoid hypoglycemia while using an ultra-long-acting insulin.