Diabetes Aerobic and Resistance Exercise (DARE) Study

Background. The incidence of type 2 diabetes mellitus in the Western world is rising rapidly due to increases in obesity and sedentary behaviour, and diabetes is among the most potent common risk factors for premature disability and mortality. Landmark clinical trials such as the UK Prospective Diabetes Study proved that these excess risks in type 2 diabetes can be reduced through relatively modest improvements in glycemic control (HbA1c difference of 0.9% over time). The excess morbidity and mortality in diabetes is attributable both to hyperglycemia and to a cluster of other metabolic disturbances associated with insulin resistance, and exercise can have beneficial effects on all of these abnormalities. The standard recommendation to people with diabetes has been to perform aerobic exercise such as brisk walking, swimming, or jogging. There is very little research on resistance exercise (such as weight lifting or exercise with weight machines) in type 2 diabetes. Resistance exercise in non-diabetic subjects increases lean body mass, resulting in increased metabolic rate, decreased insulin resistance and increased glucose disposal. Furthermore, in a recent randomized trial the addition of resistance exercise to a cardiac rehabilitation program resulted in marked improvements in quality of life, to a far greater extent than seen with aerobic exercise alone. For these reasons, we feel that resistance exercise in type 2 diabetes is a modality worthy of further research. A pilot study of our present proposal, funded by the Canadian Diabetes Association (CDA) is in progress; compliance has been excellent with >90% attendance.

Primary research question: In patients with type 2 diabetes, does a 6-month resistance or aerobic training program result in improved glycemic control as reflected in reduced hemoglobin A1c (HbA1c)? Is the effect of one type of exercise additive to that of the other?

Secondary research questions: In patients with type 2 diabetes, what are the effects of each exercise modality on:

1. Body composition (assessed using gold-standard methods including CT scan and deuterium oxide), resting energy expenditure (using indirect calorimetry) and insulin resistance? To what extent do changes in these parameters mediate changes in HbA1c?
2. Important nontraditional metabolic CHD risk factors (LDL particle diameter, plasma insulin, apoprotein B, c-reactive protein, free fatty acids) and traditional metabolic CHD risk factors (HDL-C, LDL-C, triglycerides, total/HDL cholesterol ratio, BP)?
3. Health-related quality of life (QOL) as measured by the Well-Being questionnaire or the SF-36? Does modality of exercise or change in quality of life from baseline to 6 months predict frequency of exercise during the 6 months following the intervention?

Study design: Randomized controlled trial. After a 4-week supervised low-intensity exercise run-in period to test compliance, previously inactive Type 2 diabetic subjects not currently engaging in regular exercise are randomized to 4 arms: aerobic exercise 3X per week, resistance exercise 3X per week, both combined or waiting-list control. The exercise intervention takes place at YMCA branches in metropolitan Ottawa. Exercise is closely supervised and progressive in intensity and duration. Compliance is verified through direct supervision, completion of detailed exercise logs, and central automated electronic tracking of YMCA attendance through scanning of membership cards. Primary outcomes are measured at 6 months. At the end of 6 months subjects are given a maintenance program and reexamined 6 months later to assess the durability of any benefits from the exercise program. During the 6 month intervention period diet is standardized using repeated sessions with a dietitian, and doses of medications altering glucose, lipids and BP are held constant unless change is medically urgent.

Significance: The global burden of type 2 diabetes is increasing, and complications of the illness occur primarily in those whose glycemic control is fair or poor. If appropriately selected exercise training improves glycemic control and is adopted by more patients, it is likely that the morbidity associated with type 2 diabetes will be decreased. This is particularly true if such training also improves quality of life, and more people are thus inclined to continue exercising in the long term.