Early Follicular Phase of the Menstrual Cycle May Be Associated With More Post-Exercise Hyperglycemia in Female Participants With Type 1 Diabetes

Abstract

Despite substantial health benefits of exercise in people with type 1 diabetes (T1D), significant knowledge gaps exist around blood glucose (BG) responses to exercise in females with T1D, especially with regards to the menstrual cycle. We compared the impact of aerobic exercise on continuous glucose monitoring (CGM) glucose between the early follicular and late luteal phases of the menstrual cycle in 7 female participants with T1D (mean±SD: age 31±10 years, A1C 7.1±0.5%, VO2peak 33.2±4.3 mL/kg/min). Participants had regular menstrual cycles and were not using hormonal contraceptives. In each phase, participants performed moderate aerobic exercise (cycling at 50% of pre-determined VO2peak) for 45 minutes on an ergometer starting at 5 pm. Meal timing/composition and insulin dosage were kept as consistent as possible between sessions. Blood glucose was measured using CGM for 24 h before exercise and 24 h post exercise. There were no significant differences in mean CGM glucose between the two phases during the 24 h pre, 0-6 h post, overnight (midnight to 6 am) post, or 24 h post exercise. Mean CGM glucose was significantly higher 24 h post as compared to 24 h pre exercise (9.0±1.7 vs 7.3±1.6 mmol/L) in the follicular phase (p=0.0468). There were more post-exercise hyperglycemic episodes in the follicular phase compared with the luteal (2.9±1.7 vs 1.1±0.7, p=0.0453). Female T1D participants may be more prone to post-exercise hyperglycemia requiring insulin correction during the follicular phase of the menstrual cycle.