The VIGORous Physical Activity for Glycaemic Control in Type 1 Diabetes (VIGOR) Trial (VIGOR)

Background/Justification: Regular physical activity (PA) has substantial health benefits in persons with type 1 diabetes (T1D), including reduced risk of complications and cardiovascular mortality. Despite these benefits, individuals with T1D remain significantly less active than their peers without diabetes. Two major factors likely explain the low rates of PA in young people with T1D: (1) fear of post-exercise hypoglycaemia, particularly nocturnal hypoglycaemia, and (2) a lack of empirical evidence for the efficacy of PA for achieving optimal glycaemic control. A number of acute exercise trials recently demonstrated that the inclusion of vigorous intensity PA in conventional moderate intensity (i.e. walking) PA sessions may overcome these limitations. No studies have tested the efficacy of high intensity PA for reducing the risk of exercise-related hypoglycaemia or glycaemic variability in a randomized controlled trial (RCT). Study Hypotheses: In persons 15-35 years of age living with T1D, this study will test the hypotheses that (1) the addition of intermittent vigorous intensity PA to a moderate intensity intervention will reduce the time spent in hypoglycaemia in the 12 hour period following exercise and (2) the addition of intermittent vigorous intensity PA to a moderate intensity PA intervention will elicit significant improvements in glycemic excursions, as measured by the Mean Amplitude of Glycaemic Excursions (MAGE), in the 12-hour period following exercise.We are also exploring the hypothesis that reducing the risk of hypoglycemia will lead to a sustained increase in physical activity one year after randomization.

Type 1 Diabetes, Hypoglycaemia, Glycaemic variability, Vigorous Intensity Physical Activity, Continuous Glucose Monitoring

150-200 minutes of weekly moderate intensity exercise, with short bouts of vigorous intensity exercise (80-90% of peak fitness)

Time Spent in Hypoglycaemia in the 12-hour Period Following Exercise, Defined as an Interstitial Glucose Reading <4.0mmol/L and Measured by Continuous Glucose Monitor.

Glycaemic Variability, Measured by the Mean Amplitude of Glycaemic Excursions (MAGE), in the 12-hour Period Following Exercise. This is Calculated From the Same Continuous Glucose Monitor Data as the Primary Outcome.

Inclusion Criteria: Age: 15-45 years old Have lived with type 1 diabetes for at least 2 years HbA1c <9.9% Currently physically inactive (<150 minutes of self-reported structured physical activity per week) Undergone a resting ECG to screen for left ventricular hypertrophy, arrhythmias or signs or coronary artery disease that may be exacerbated with vigorous intensity exercise Exclusion Criteria: Have frequent and unpredictable hypoglycaemia Had a change in insulin management strategy, including adoption of a pump, within 2 months of enrolment Are currently participating in structured activity or sport-related activities Are women who are pregnant or planning to get pregnant within the 12 months of the trial and those who are breastfeeding Have conditions that would render physical activity contraindicated including: uncontrolled hypertension (BP>150mmHg systolic or >95mmHg diastolic in a sitting position); severe peripheral neuropathy; history of cardiovascular disease Have a cognitive deficit resulting in an inability to provide informed consent Currently taking beta blockers Currently taking atypical antipsychotics or corticosteroids