Trends of glucose, lactate and ketones during anaerobic and aerobic exercise in subjects with type 1 diabetes: The ACTION-1 study.

BACKGROUND: Exercise is part of type 1 diabetes (T1D) management due to its cardiovascular and metabolic benefits. However, despite using continuous glucose monitoring, many patients are reluctant to exercise because of fear for hypoglycaemia. AIMS: We assessed trends in glucose, lactate and ketones during anaerobic and aerobic exercise in people with T1D and compared incremental area under the curve (AUC) between both exercises. METHODS: Twenty-one men with T1D (median [IQR]: age 29 years [28-38], body mass index (BMI) 24.4 kg/m2 [22.3-24.9], HbA1c 7.2% [6.7-7.8]), completed a cardiopulmonary exercise test (CPET) and a 60-min aerobic exercise (AEX) at 60% VO2 peak on an ergometer bicycle within a 6-week period. Subjects consumed a standardised breakfast (6 kcal/kg, 20.2 g CHO/100 ml) before exercise without pre-meal insulin and basal insulin for pump users. RESULTS: During CPET, glucose levels increased, peaking at 331 mg/dl [257-392] 1-3 h after exercise and reaching a nadir 6 h after exercise at 176 mg/dl [118-217]. Lactate levels peaked at 6.0 mmol/L [5.0-6.6] (max 13.5 mmol/L). During AEX, glucose levels also increased, peaking at 305 mg/dl [245-336] 80 min after exercise and reaching a nadir 6 h after exercise at 211 mg/dl [116-222]. Lactate levels rose quickly to a median of 4.3 mmol/L [2.7-6.7] after 10 min. Ketone levels were low during both tests (median ≤ 0.2 mmol/L). Lactate, but not glucose or ketone AUC, was significantly higher in CPET compared to AEX (p = 0.04). CONCLUSIONS: Omitting pre-meal insulin and also basal insulin in pump users, did prevent hypoglycaemia but induced hyperglycaemia due to a too high carbohydrate ingestion. No ketosis was recorded during or after the exercises. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov: NCT05097339.