Effects of a 50% versus 100% pre-prandial insulin bolus reduction to improve glycemic safety during postprandial continuous and intermittent exercise in adults with type 1 diabetes treated with multiple daily injections.
This study aimed to evaluate the effect of a 50% reduction in preprandial bolus insulin (50%-B) on plasma glucose (PG) responses during postprandial exercise of continuous moderate intensity (CONT) and intermittent high intensity (INT) in individuals with type 1 diabetes (T1D).
Sixteen adults with T1D (31% male), treated with multiple daily insulin injections (MDI), participated in a randomized crossover study comprising four experimental conditions, separated by a washout period of at least 48 hours. Participants performed two 30-minute, preceded by a 3-minute warm-up without weights:• CONT: continuous cycling at 60% of maximal aerobic power (MAP).• INT: 2-minute intervals alternating between 40% and 80% of MAP, repeated for 7 intervals, with the last interval adjusted so that the total exercise time is exactly 30 minutes. Each exercise modality was performed under two insulin conditions: a full preprandial bolus (100%-B) and a 50% reduction (50%-B). Plasma glucose, insulin, and cortisol were measured before, during, and after exercise. Linear mixed models were used to analyze temporal changes and condition effects.
Blood glucose decreased significantly over time for both exercise types (p < 0.001). During CONT, the decline in PG was similar between doses (Δ100%-B: -3.01 ± 2.96 vs. Δ50%-B: -2.82 ± 2.28 mmol/L; p = 0.18), However, the nadir PG was higher with 50%-B compared to 100%-B (8.59 ± 4.07 vs. 5.69 ± 3.06 mmol/L, respectively; β = +2.91 mmol/L; p = 0.026), and hypoglycemia was less frequent (2 vs. 18 episodes; p = 0.028). During INT, PG decreased less with 50%-B than with 100%-B (Δ: -2.03 ± 1.63 vs. -3.62 ± 2.76 mmol/L; p = 0.022), with no hypoglycemic episodes under 50%-B compared to six with 100%-B. Mean PG remained higher with 50%-B across both exercise types (p < 0.01). Plasma insulin decreased over time (p = 0.038) regardless of bolus condition, while cortisol increased more during INT with 100%-B than with 50%-B (p = 0.02).
Reducing the preprandial bolus insulin by 50% effectively attenuates exercise-induced declines in plasma glucose and substantially reduces hypoglycemia risk, particularly during intermittent high-intensity exercise. These results emphasize the clinical relevance of personalized insulin adjustments to enhance metabolic safety during exercise in individuals with T1D.
Sixteen adults with T1D (31% male), treated with multiple daily insulin injections (MDI), participated in a randomized crossover study comprising four experimental conditions, separated by a washout period of at least 48 hours. Participants performed two 30-minute, preceded by a 3-minute warm-up without weights:• CONT: continuous cycling at 60% of maximal aerobic power (MAP).• INT: 2-minute intervals alternating between 40% and 80% of MAP, repeated for 7 intervals, with the last interval adjusted so that the total exercise time is exactly 30 minutes. Each exercise modality was performed under two insulin conditions: a full preprandial bolus (100%-B) and a 50% reduction (50%-B). Plasma glucose, insulin, and cortisol were measured before, during, and after exercise. Linear mixed models were used to analyze temporal changes and condition effects.
Blood glucose decreased significantly over time for both exercise types (p < 0.001). During CONT, the decline in PG was similar between doses (Δ100%-B: -3.01 ± 2.96 vs. Δ50%-B: -2.82 ± 2.28 mmol/L; p = 0.18), However, the nadir PG was higher with 50%-B compared to 100%-B (8.59 ± 4.07 vs. 5.69 ± 3.06 mmol/L, respectively; β = +2.91 mmol/L; p = 0.026), and hypoglycemia was less frequent (2 vs. 18 episodes; p = 0.028). During INT, PG decreased less with 50%-B than with 100%-B (Δ: -2.03 ± 1.63 vs. -3.62 ± 2.76 mmol/L; p = 0.022), with no hypoglycemic episodes under 50%-B compared to six with 100%-B. Mean PG remained higher with 50%-B across both exercise types (p < 0.01). Plasma insulin decreased over time (p = 0.038) regardless of bolus condition, while cortisol increased more during INT with 100%-B than with 50%-B (p = 0.02).
Reducing the preprandial bolus insulin by 50% effectively attenuates exercise-induced declines in plasma glucose and substantially reduces hypoglycemia risk, particularly during intermittent high-intensity exercise. These results emphasize the clinical relevance of personalized insulin adjustments to enhance metabolic safety during exercise in individuals with T1D.
Authors
Lahouel Lahouel, Mnif Mnif, Bouzid Bouzid, Hadj Kacem Hadj Kacem, Heyman Heyman, Rabasa-Lhoret Rabasa-Lhoret, Frikha Frikha, Zouari Zouari, Lespagnol Lespagnol, Rekik Rekik, Turki Turki, Tagougui Tagougui
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