Mitigating the effects of sitting on vascular dysfunction in type 2 diabetes: the MOVE trial

This randomised crossover trial in overweight or obese adults diagnosed with type 2 diabetes will involve three acute experimental conditions (each of 8 hours duration; 1 hour to achieve steady state and a 7 hour experimental period beginning when breakfast is served) to examine the impact of prolonged uninterrupted sitting, or breaking up sitting with brief bouts of simple resistance activities on endothelial function. Twenty four inactive and injury-free participants aged between 35-70 years will be recruited. Participants will visit the Physical Activity Laboratory at the Baker Heart and Diabetes Institute on 4 separate occasions. Participants will initially be screened for eligibility via a telephone-administered interview, with likely candidates invited to attend a medical screening & familiarisation at the Baker. During the visit participants will be able to ask further questions prior to giving signed consent to participate. The medical screening will consist of a medical examination by the study physician, resting 12 lead electrocardiogram and a point-of-care HbA1c test (finger prick) to determine eligibility immediately. After eligibility has been confirmed, participants will proceed to the familiarisation part of visit 1. In order to ensure optimal safety and to allow orientation with the testing procedures and measurement devices, the study staff will familiarize participants with simple resistance activities, ensuring they are comfortable with the exercises and suitable technique and movement consistency are achieved. Anthropometric measurements (weight, height and waist circumference) will be obtained and participants will be shown the FMD procedure. Participants will be instructed not to alter their habitual pattern of daily activities while involved in the trial. To minimise any potential diet-induced variability in the metabolic profile, participants will be provided with a standard ‘food pack’, containing a dinner meal for the night prior to each experimental condition, and dinner and breakfast following the experimental condition. All food packs will be matched or macronutrient composition (as % of total energy intake, with a macronutrient profile of 53-55% energy from carbohydrate, 12-15% energy from protein, and 30-33% energy from fat). Participants will be instructed to consume only the food items within the food pack for the dinner meal prior to the experimental condition, between 7-9pm that evening, and to then fast until the trial condition the next morning. They will also be asked to record their food and fluid intake in a food diary and to avoid and moderate and/or vigorous intensity activity for at least 72 hours prior to each experimental condition. To assess compliance and habitual physical activity, participants will be fitted with two objective activity monitors at the familiarisation session – an accelerometer (Actigraph model GT3X+) worn on the wrist, and an inclinometer (activPAL3TM) worn on the thigh, which will be worn for the week prior to each condition. The objective activity monitoring will be used in combination with an activity diary. At this visit participants will also be fitted with an Abbott Freestyle Libre Flash Glucose Monitoring system (Abbott Diabetes Care, Australia) with a sensor worn on the back of the upper arm. Flash glucose monitoring involves scanning the sensor with a reader device to upload glucose data approximately 4 times daily, with no need for finger prick calibrations. Participants will wear this system for the duration of the study, with a new sensor fitted at the beginning of the second experimental visit. Each participant will then complete three experimental conditions in a laboratory setting, supervised by the study staff to ensure adherence to the experimental conditions. The three conditions will be separated by a minimum 6-day washout period to account for any residual physiological effects of the intervention. Participants will be advised to wear appropriate footwear and clothing to allow sufficient range of motion at the knee and hip (45 degrees to 90 degrees for half-squats or knee raises). In all experimental conditions participants will be seated in a comfortable lounge-chair and have access to a television, DVD player and reading materials such as newspapers and magazines. They will be instructed to minimise excessive movement, but will be allowed to visit the toilet (via wheelchair) when necessary. Before starting the experimental conditions, participants will sit for the first hour, during which baseline blood pressure measurements will be taken. An in-dwelling venous cannula will be inserted, and a baseline blood sample drawn. Participants will be then given a standardised breakfast meal comprised of 33% of estimated daily energy requirements, with a macronutrient profile of 53-55% energy from carbohydrate, 12-15% energy from protein, and 30-33% energy from fat and the activity protocols begin. The two activity interventions are; A) Simple Resistance Exercises and Interrupted Sitting (30): Participants will complete a 3 min bout of simple resistance activities every 30 minutes, remaining seated at all other times (except for toilet breaks). The activities will be allocated into nine 20 second segments, alternating between body weight half squats, calf raises and brief gluteal contractions in-between single leg knee raises (total exercise time equals to 36 mins). This interchange between movements will provide rest for the corresponding muscle groups between each activity segment. To ensure appropriate standardisation, participants will complete each activity in a controlled manner within their range of motion (knee or hip 45 to 90 degrees for half-squats or knee raises), while synchronizing the tempo of each activity to a demonstration video playing. B) Simple Resistance Exercises and Interrupted Sitting (60): As for condition A, except participants complete a 6 minute bout of simple resistance activities every 60 minutes throughout the 7 hour experimental period. This procedure will be completed on 6 occasions, totalling 36 minutes of activity. The simple resistance activities will follow exactly the same procedure as condition A, except each bout will last for 6 min. Before leaving the laboratory on the experimental days, participants will be fitted with a 24 hour ambulatory blood pressure monitor (ABPM) to be worn until noon the following day in addition to the Libre. Participants will be asked to keep these devices on overnight after each trial to assess what happens to their blood glucose and blood pressure during this period. After the final study visit, the participant will remove both devices and mail back to the Baker in a provided parcel post bag.