Glucose responses during aerobic exercise showed clear variability in adults with type 1 diabetes mellitus (T1DM). A study in Diabetes Technology & Therapeutics examined how pre-exercise glucose and menstrual cycle phase influenced glycemic patterns during moderate-intensity activity.

The analysis included 51 aerobic sessions from adults treated with multiple daily insulin injections. Each 30-minute session was performed at moderate intensity. Data included plasma and interstitial glucose, heart rate, and anthropometric measures. Women completed exercise sessions during both follicular and luteal phases. Glucose trajectories were clustered using k-medoids and Dynamic Time Warping to identify recurring glucose patterns.

Two distinct glucose responses were identified: descending and stable. Higher pre-exercise glucose was associated with greater glucose decline and increased risk of hypoglycemia, with the strongest effect in men. Women more often demonstrated stable profiles, especially during the luteal phase. Fitness level and body composition also influenced cluster assignment, with fitter individuals more likely to show stable patterns. Pre-exercise glucose was the strongest predictor overall. Menstrual cycle phase produced a modest but meaningful influence on glucose dynamics.

These findings highlight substantial physiological variation in exercise responses in T1DM. They support exercise guidance tailored to glucose level, sex, fitness, and menstrual cycle phase and highlight the need to include these factors in insulin-dosing models.