Any exercise can help us control our diabetes. But when we get 45 minutes each of aerobic exercise and resistance training for just three days a week, we can reduce our A1C a lot. In fact, this combination works about as well as any prescription drug can.
People with diabetes who worked out half the time on a treadmill or bicycle ergometer -- the aerobic exercise in a recent study -- and lifted weights -- the resistance training -- saw their A1C levels drop almost 1 percent in a 22-week program. These encouraging results come from a randomized controlled trial of 251 people with type 2 diabetes reported in the Annals of Internal Medicine. Ronald Sigal, M.D., an endocrinologist and associate professor at the University of Calgary's department of medicine, led this study, the largest ever on the effectiveness of aerobic exercise and resistance training.
Our A1C level is the best measure of diabetes control that we have. Some people seem to think that reducing it 1 percent isn't much. But since the A1C is itself a measure of the percentage of glucose stuck to the hemoglobin protein in our red blood cells, it can mean our having an out-of control A1C level of 8.0 come down to 7.0. And going from a satisfactory level of 7.0 to normal level of 6.0 can be huge.
Either aerobic exercise or resistance training brought down the A1C levels of the people in this trial. Those in the resistance training group brought down their level a good deal -- an average of 0.38 percentcompared with a sedentary control group. But aerobic exercise was better, reducing A1C an average of 0.51 percent. The combined group achieved the best results by bringing their level down 0.97 percent.
The researchers also studied changes in lipid results -- total cholesterol, HDL cholesterol, LDL cholesterol, and triglyceride levels -- as well as blood pressure. Surprisingly, however, they didn't find any statistically significant changes here.
The people in the study who saw their A1C levels drop the most were those who had higher A1C levels at the beginning of the study. "If glycemic control is poor, either aerobic or resistance training alone would also improve the hemoglobin A1C value, but the combination of these forms of exercise would be better," the study's authors concluded.
Older participants in the study seemed to benefit more from resistance training than the younger ones did. That was probably because they have lost more muscle mass through disuse.
The group who had lower A1C levels when the study began benefited only from the combined aerobic and resistance training.
Was it just because the combined group exercised twice as much that their A1C levels turned out about twice as good? Dr. Sigal and his colleagues recognize that this is a limitation of the study.
"However, because the physiologic effects of aerobic training differ from those of resistance training," they add, "we cannot assume that our results reflect only additional exercise time. Aerobic training involves continuous activity of multiple large muscle groups, whereas resistance training involves isolated, brief activity of single muscle groups."
In any case, combining aerobic exercise and resistance training is more sustainable. Lots of people, myself included, would find that doing 90 minutes of just one type of exercise three times a week to be monotonous -- unless it is hiking in the mountains, which gives me limitless exercise and pleasure.
All of us, however, get complementary benefits from aerobic and resistance exercise. Aerobic exercise increases our cardiorespiratory fitness, and resistance training increases our muscle strength and endurance. Together that's the best exercise.