Effect of Continuous vs Intermittent Aerobic Exercise on Glycemic Control in a Barbadian Population With Type 2 Diabetes

With the background that there is increasing evidence that breaking up sedentary time with physical activity may be potentially associated with improved blood glucose levels (Francois et al., (2014) & van Dijk et al., (2013), this study aims to investigate and compare the effect of a single 30-minute bout of moderate intensity aerobic exercise to the effect of three 10-minute pre-prandial bouts of energy-matched and volume-matched aerobic exercise on 2-hr post prandial and fasting blood sugar levels in a sample of type 2 diabetes patients.

Different from previous studies, this research seeks to evaluate these effects in a Black Caribbean population, in a type 2 diabetes population on medication including insulin and also seeks to evaluate if either exercise regimen is indeed palatable to the target population by evaluating treatment acceptability.

The proposed study will be a crossover randomized controlled study. There will be two intervention groups - a single 30-minute bout of moderate intensity aerobic exercise before breakfast and three (3) 10-minute bouts of moderate intensity aerobic activity before breakfast, lunch and dinner. The primary outcome measure will be 2-hr post prandial blood sugar levels and fasting blood sugar levels on the day following the intervention. Neither subject nor investigator will be blinded to the intervention.

Subjects will include patients with a documented diagnosis of type 2 diabetes, that is a documented HbA1C ≥ 6.5%. Baseline data will include body mass and body composition and will be measured using the bioelectrical impedance technique (Tanita scale). Waist circumference will be assessed using a Gulick tape measure. Baseline sedentary behaviour and physical activity level will be assessed using the validated International Physical Activity Questionnaire.

All recruited subjects will be asked to complete two exercise interventions separated by a one-week washout period: 1) a single 30-minute bout of moderate intensity aerobic exercise before breakfast and 2) three (3) 10-minute bouts of moderate intensity aerobic activity before breakfast, lunch and dinner. Each subject will be randomized to one of two treatment sequences: single bout followed by multiple bouts (S-M) or multiple bouts followed by single bout (M-S). The randomization will be done using online statistical computing web programming (www.randomization.com) to generate a randomization schedule with balanced permutations.

Timing between exercise completion and commencement of meal intake will be approximately 15 minutes. A heart rate reserve range of 40-59% will be used to define moderate intensity. Heart rate will be measured using a validated Polar heart rate monitor. Rate of perceived exertion will be a secondary measure of exercise intensity.

Two-hour (2hr) post prandial blood sugar levels and fasting blood sugar levels on the day following the exercise intervention will be measured using a validated capillary blood glucose meter. Blood pressure will also be measured at the same times that blood glucose values are taken using a validated automated blood pressure machine.

Standardized meals of fixed nutrient content and individualized to the subject's calculated estimated daily caloric requirements will be provided to subjects on the day of the exercise interventions. Treatment acceptability will be assessed following each exercise intervention using an expert-designed questionnaire that will be piloted in this study.