In a new randomized controlled trial, both aerobic and resistance exercise improved glycemic/blood sugar control in people with type 2 diabetes. The greatest improvements came from combined aerobic and resistance training.
The study included 251 adults, between ages 39 and 70, who were not exercising regularly and had type 2 diabetes. Participants were assigned to one of four groups: performing 45 minutes aerobic training three times per week, 45 minutes of resistance training three times per week, 45 minutes each of both three times per week, or no exercise.
Each participant was evaluated on changes in A1c value, a number that reflects blood sugar concentrations over the previous two or three months, and is expressed as a percent. An absolute decrease of 1.0 percent in A1c value (e.g. from 8.5 percent to 7.5 percent) would be associated with a 15 percent to 20 percent decrease in risk of heart attack or stroke, and a 25 percent to 40 percent decrease in risk of diabetes-related eye disease or kidney disease.
Both the aerobic and resistance training groups had improved blood sugar control A1c value decreased by about 0.5 percent. The group that did both kinds of exercise had about twice as much improvement as either other group alone--A1c value decreased by 0.97 percent compared to the control group. The control group that did not exercise had no change in A1c value.
"We know that aerobic exercise improves glycemic control," said Ronald Sigal, MD, the lead author of the study. "But we didn't really know too much about what kind of exercise is the most beneficial and how much of it. In particular there wasn't much known about resistance exercises when we started planning this study. At the time, some thought that resistance exercise is not useful or even dangerous for some people with diabetes."
Dr. Sigal, now an associate professor of medicine and cardiac sciences at University of Calgary, oversaw the 26-week study, conducted in centers in Canada.
"And even for people who had fairly good blood sugar control at the beginning of our study, those who did both aerobic and resistance exercise had further improvements in glucose control."
"The bottom line," said Dr. Sigal, "is that doing both aerobic and resistance exercise is the way to maximize the effects of exercise on blood glucose control in type 2 diabetes."
In an accompanying editorial, William E. Kraus, MD and Benjamin D. Levine, MD, say, "Imagine an inexpensive pill that could decrease the hemoglobin A1c value by 1 percentage point, reduce cardiovascular death by 25 percent, and substantially improve functional capacity (strength, endurance, and bone density). Diabetes experts would be quick to incorporate this pill into practice guidelines and performance measures for diabetes. (These) study results should simulate all clinicians to include exercise assessment and counseling into every clinic visit."
The study, "Effects of Aerobic Training, Resistance Training, or Both on Glycemic Control in Type 2 Diabetes," and the editorial, "Exercise Training for Diabetes: The "Strength" of the Evidence," will be published in the in the Sept. 18, 2007, edition of Annals of Internal Medicine.
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