Impact of timing, type, and intensity of physical activity on glycemic outcomes in a cohort of well-controlled youth with type 1 diabetes

Aims: To evaluate how the timing, type, and intensity of bout-related physical activity (PA) influence glycemic control across age groups in youths and young adults with type 1 diabetes (T1D). Materials and methods: In this cross-sectional study, 100 insulin pump-treated individuals with T1D (55 females; mean age 16.6 ± 6.6 years; HbA1c 6.8 ± 1.0%) were monitored for 7 days using self-reported training logs and continuous glucose monitoring. Participants were categorized by age (< 14, 14-17, 18-31 years) and by exercise timing (morning, afternoon, evening), type (aerobic, anaerobic, mixed), and intensity (low, medium, high). Glycemic variables included mean glucose, time in range (TIR), time below range (TBR), time in level 2 hypoglycemia, time above range (TAR), time > 250 mg/dL, and total daily insulin dose. Results: Exercise timing and intensity had greater effects on glycemic outcomes than exercise type. Afternoon activity was associated with improved TIR and reduced TAR in younger participants, whereas morning exercise in adolescents was linked to higher TBR. Higher-intensity exercise was associated with greater TAR in adolescents whereas no significant differences in glycemic outcomes were found by exercise type. Conclusions: The timing and intensity of exercise significantly influence glycemic responses in youths with T1D, with notable age-related differences. Personalized PA recommendations should consider these factors to optimize glycemic outcomes.