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/m(2) [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% VO(2)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