Exercise and Blood Glucose Levels in Patients With Type I Diabetes - a Pilot Study

Background: During and after exercise there is a twofold stimulation of glucose transporter type 4 in type 1 diabetes mellitus (T1DM) caused by an exogenous insulin injection and muscle contraction. In case of no insulin reduction before exercise and/or an additional carbohydrate supplement patients with T1DM would become hypoglycemic. There are no specific data dependent on individual exercise intensities and strategies of bolus insulin reduction. The aim of the present study is to avoid hypoglycemia during and after exercise and to calculate a critical time where blood glucose would decrease to 50% of baseline by a pre exercise standardized insulin regimen during standardized cycle ergometer exercises dependent on different modes, intensities and energy expenditures as well as counter regulatory hormones.

Methods/design: Participants consist of 7 male subjects aged 18 to 35 years with T1DM (fasting C-peptide (≤ 0.3 nmol/l), HbA1c ≤ 64 mmol/mol). After a four-weeks basal insulin adaptation of ultralong-acting basal insulin (Novo Nordisk) each subject will perform a maximal incremental cycle ergometer exercise test with a reduction of short time insulin of 40% to determine the individual aerobic/anaerobic threshold called first/second lactate turn point (LTP1, LTP2). Four constant load and three high intensity intermittent cycle ergometer exercise tests (30min) will be performed at 5% Pmax below and above LTP1 and LTP2 (at 5% above LTP2 no high intensity intermittent cycle ergometer exercise test) with a reduction of short time insulin doses (standardized breakfast-four hours before each test) of 25% at 5% Pmax below LTP1 and 50% at 5% Pmax above LTP1 and 75% at 5% Pmax below and above LTP2 with one week interception between testing. 24h before testing subjects will be fitted with a continuous glucose monitoring system for at least 48h. Primary outcomes include blood glucose decrease from baseline during constant load tests, energy expenditure during testing, 24h CGMS measurements and hormones catecholamines, cortisol, glucagon and insulin growth factor 1. Secondary outcome measurements include heart rate, lactate and respiratory gas exchange values.

Discussion: If the results confirm the hypothesis, this study could be one of the first recommendations for T1DM patients, how to adapt bolus insulin dose individually before defined exercises without the risk hypoglycemia during and after exercise.