Every day, it seems, exercise is touted in newspapers or magazines as a critical part of a healthy lifestyle. That's a good generalization. But what are some of the specific benefits of exercise?

Dr. Ron Sigal's research, which has taken him from the bench to the bedside, will provide some answers to these questions. His main research interest is in the use of lifestyle measures such as exercise for prevention of cardiovascular disease and diabetic kidney disease, the most deadly complications of diabetes. In one of two clinical trials under his direction, he is investigating whether regular physical activity can slow the progression of kidney disease in diabetics. People with early diabetic kidney disease who have enrolled in the trial are randomly assigned to one of two groups. The first group receives one-on-one education on diabetes, plus a supervised home-based walking program, while the other receives the same education program but without the exercise component. Frequent follow-up phone calls to provide encouragement and support are made to those in the first group, as this has been shown to increase adherence to exercise. Ultimately, the trial will enroll approximately 100 patients between the ages of 18 and 79.

The second clinical trial compares the benefits of different types of exercise in diabetes. The two main types of exercise are resistance training (for example, weight lifting), in which muscular strength is used either to move a weight or against a resistive load, and aerobic training (such as walking or cycling), which increases cardiorespiratory endurance. In people with type 2 diabetes, regular aerobic exercise improves blood sugar control. Unfortunately, many people who start aerobic training programs do not continue them for more than a few months. As for resistance training, very little research has been done in this population. In nondiabetic subjects, resistance exercise increases lean body mass, resulting in increased metabolic rate, decreased insulin resistance, and increased glucose disposal, all of which would be beneficial for diabetics. 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, Dr. Sigal feels that resistance exercise in type 2 diabetes is worthy of further research. He is collaborating in this trial with Dr. Glen Kenny of the University of Ottawa School of Human Kinetics, Dr. Robert Reid of the University of Ottawa Heart Institute, and fellow Loeb researcher, economist Douglas Coyle.

In this study, type 2 diabetic patients not already engaging in regular exercise are randomly assigned to one of four groups, engaging either in aerobic exercise three times per week, in resistance exercise three times per week, in both combined, or in a waiting-list control group. The exercise is supervised at YMCA branches in metropolitan Ottawa, and progresses in intensity and duration. After six months, the patients subjects are given a maintenance training program. After a further six months, they are reexamined to assess the durability of any benefits from the exercise program. Blood sugar control, quality of life, muscle gain, and fat tissue loss will all be measured. Dr. Sigal believes that if resistance training improves blood sugar control, promotes fat loss and is adopted by more patients, it is likely that the complications associated with type 2 diabetes will be decreased. This is particularly likely if resistance training also improves quality of life, and more people are thus inclined to continue exercising in the long term.

Gestational diabetes, which occurs during pregnancy and disappears after delivery, also interests Dr. Sigal. Women who develop this disorder have a high risk of developing type 2 diabetes five to ten years later. The fact that those with type 2 diabetes often have lipid disorders led Dr. Sigal to wonder whether women with gestational diabetes do too. Therefore, he analyzed data on women who were seen at the Royal Victoria Hospital's Diabetes in Pregnancy Clinic over a five-year period. Lipids (cholesterol and triglycerides) taken from these women at six weeks after pregnancy were compared with lipids taken at six weeks after pregnancy from a control group. Total cholesterol levels were found to be almost identical for both groups, yet levels of HDL (the "good" cholesterol) were lower in the gestational diabetes group and triglycerides were higher. When Dr. Sigal compared lipid concentrations among the clinic patients, he found the samples fell into three subgroups, according to whether, after pregnancy, the women's glucose tolerance was normal, impaired, or diabetic. Further, the lower the woman's glucose tolerance, the lower her level of HDL and the higher her triglyceride level. Insulin resistance followed a similar pattern, increasing with decreased glucose tolerance. Dr. Sigal concluded that women with gestational diabetes should therefore have intensified screening for heart disease risk factors, especially if impaired glucose tolerance or diabetes persists after childbirth.

In a recently completed study, Dr. Sigal collaborated with Health Canada's Laboratory Centres for Disease Control to determine the extent to which people visiting the diabetes clinic were immunized against influenza and pneumococcus. Both vaccinations are recommended for adults with diabetes, and are provided free by the province. Dr. Sigal's team distributed questionnaires to clinic patients, asking whether they had received the vaccinations. Other questions revealed the factors associated with the likelihood of a patient's having been immunized. Results indicate that those over age 65, or who have other diabetic complications, were the most likely to have received both vaccines. Interestingly, those with post-secondary education were generally less knowledgeable about the vaccines, and less likely to have had them. However, among this subgroup, those with post-secondary education who were knowledgeable about the vaccines were more likely to have been vaccinated than their counterparts without post-secondary education.

Dr. Sigal is involved in other diabetes initiatives. He recently published an invited evidence-based review of Diabetes and Cardiovascular Disease in the new British Medical Journal/American College of Physicians publication Clinical Evidence 1999, and will update this review every six months. He is the Chairman of the Canadian Diabetes Association's task force on anti-obesity drugs. He is also the Chairperson of the Centre for Diabetes and Lipid Disorders Task Force on Medical Information Flow. In this capacity, Dr. Sigal spearheaded the development of a clinical database at the Ottawa Hospital, Civic Campus.

The global burden of type 2 diabetes is increasing. As Dr. Sigal explores the specific benefits of exercise, he is clarifying the role it can play in the prevention, diagnosis, and management of diabetes and related disorders.