Does Exercise Timing Affect Glucose Levels in People With Diabetes?

Purpose:To compare the effects of a single bout of walking conducted at different times of the day on 24-hour glucose profiles in individuals with type 2 diabetes. In addition to a control (no exercise) conditions, a bout of walking will be completed in the following 3 conditions i. in the fasted state, before breakfast, ii. 3-4 hours after lunch, and iii. 30 minutes after dinner.

Background: Recently, we developed the Exercise-Physical Activity and Diabetes Glucose Monitoring (E-PAraDiGM), which was tested at 8 different sites across Canada (ClinicalTrials.gov Identifier: NCT02834689). The original E-PAraDiGM protocol found no significant difference in 24-hour glucose levels between the exercise and seated control condition (publication in preparation). One the of the potential reasons for this could be the timing of exercise in relation to meals. There is no clear consensus as to the optimal time for exercise for individuals with type 2 diabetes. The goal of this study is to expand on the original E-PAraDiGM study by adding fasted state exercise and 30 minute postprandial exercise to the original 2 conditions (3-4 hours after lunch and seated control).

Research Design: The complete protocol will take place over two separate 6-day periods for each participant, which includes 50 minutes of exercise done in the following 4 conditions i. in the fasted state, before breakfast, ii. 3-4hrs after lunch, iii. 30 minutes after dinner, and iv. seated control. Each participant will complete each condition according to a randomized, crossover design.

Participants: Twelve individuals with T2D will be recruited at the University of Alberta. Participants will be between the ages of 30-90 years and will have been diagnosed with T2D for more than 6 months. They will also have no contraindications to exercise, no previous myocardial infarction, strokes, or coronary artery disease. Participants will not be treated with insulin or corticosteroids and they will have had no changes in diabetes medications in the last 3 months. Furthermore, participants will have no significant changes in body weight (>5%) in the last 3 months. Their blood pressure will be below 160/100 mmHg and their resting heart rate will be below 100 beats per minute.

Baseline Assessment: An initial visit will be used to perform screening, obtain written informed consent, and collect baseline data, including: anthropometry (e.g., height, weight, waist/hip circumference), medical history (e.g., duration of diabetes, medications), exercise history (i.e., Godin Leisure Time Exercise Questionnaire), as well as HbA1c, lipids in last 6 months and Creatinine within last year. We will also measure HbA1c with a point of care device (DCA vantage) which requires a single drop of blood (similar demands as a capillary glucose measurements that people with diabetes perform routinely). Body composition with be estimated with bioelectrical impedance analysis (BIA, Tanita TBF-300A). During this initial visit, participants will also have the opportunity to practice walking on a treadmill at the speed and grade that will be assigned during the intervention period (5.0km/hr at a grade of 0.5%).