Undoubtedly, every family physician who cares for patients with type 2 diabetes knows the value of regular physical activity in helping these patients manage their disease. Now a new study suggests that combining aerobic exercise with resistance training may offer benefits exceeding those achieved with either of these activities alone.
Exercise Combo Best for Patients With Diabetes, Says Study
By Barbara Bittner
11/21/2007
Published in the Sept. 18 issue of Annals of Internal Medicine, the study, "Effects of Aerobic Training, Resistance Training, or Both on Glycemic Control in Type 2 Diabetes," evaluated Canadian adults ages 39 to 70. Researchers wanted to determine the comparative effects of aerobic exercise alone, resistance training alone, and combined aerobic and resistance training on hemoglobin A1c values in patients with type 2 diabetes.
Study's Nuts and Bolts
Participants were randomized into aerobic training-only, resistance training-only, combined exercise training and control groups. All members of the exercise groups were given a free six-month membership to an exercise facility; their exercise was supervised weekly for the first four weeks and biweekly after that. Members of all exercise groups participated in three weekly sessions.
Patients in the aerobic group exercised for 15 to 20 minutes at 60 percent of maximum heart rate per session at first, working up to 45 minutes at 75 percent of maximum heart rate per session. Those in the resistance group performed seven different exercises each session, eventually progressing to doing two to three sets of each exercise at the maximum weight that could be lifted for seven to nine repetitions. The combined exercise group did the full versions of both programs. The frequency of direct training supervision was identical across all exercise groups. All study participants received the same level of dietary and medication intervention.
Adjusted absolute hemoglobin A1c values showed significant decreases in both the aerobic and resistance training groups compared with the control group. In the combined exercise training group, however, these rates declined by an additional 0.46 percentage point compared with the aerobic training group and by an additional 0.59 percentage point compared with the resistance training group. For participants with a baseline hemoglobin A1c value at or above the median of 7.5 percent, decreases in hemoglobin A1c value were greater than in patients whose baseline values were less than the median.
Patients in the aerobic group exercised for 15 to 20 minutes at 60 percent of maximum heart rate per session at first, working up to 45 minutes at 75 percent of maximum heart rate per session. Those in the resistance group performed seven different exercises each session, eventually progressing to doing two to three sets of each exercise at the maximum weight that could be lifted for seven to nine repetitions. The combined exercise group did the full versions of both programs. The frequency of direct training supervision was identical across all exercise groups. All study participants received the same level of dietary and medication intervention.
Adjusted absolute hemoglobin A1c values showed significant decreases in both the aerobic and resistance training groups compared with the control group. In the combined exercise training group, however, these rates declined by an additional 0.46 percentage point compared with the aerobic training group and by an additional 0.59 percentage point compared with the resistance training group. For participants with a baseline hemoglobin A1c value at or above the median of 7.5 percent, decreases in hemoglobin A1c value were greater than in patients whose baseline values were less than the median.
What It Means for You, Your Patients
Stephen Spann, M.D., chair of the Department of Family and Community Medicine at Baylor College of Medicine in Houston, says that the study is going to change his practice behavior. He adds that he has always recommended aerobic exercise for his patients with type 2 diabetes, but he now will begin recommending they add resistance training to their exercise programs. The messages family physicians should take from this study, he says, is that more exercise is better and "diversification of exercise has positive effects."
However, Jeffrey Unger, M.D., assistant professor of family medicine at Loma Linda University School of Medicine in Loma Linda, Calif., has some problems with the study, including flaws in its design. First, the study paid for memberships to a gym for all participants. That simply isn't reproducible in the real world, he notes. Unger also points out that many patients with diabetes have joint pain and stiffness and cannot exercise without pain. These patients may not be willing to join a gym, so family physicians need to encourage them to walk or participate in any gentle exercise.
However, Jeffrey Unger, M.D., assistant professor of family medicine at Loma Linda University School of Medicine in Loma Linda, Calif., has some problems with the study, including flaws in its design. First, the study paid for memberships to a gym for all participants. That simply isn't reproducible in the real world, he notes. Unger also points out that many patients with diabetes have joint pain and stiffness and cannot exercise without pain. These patients may not be willing to join a gym, so family physicians need to encourage them to walk or participate in any gentle exercise.
His greatest problem with the study is that patients only exercised three times per week. Both the American Diabetes Association and the Canadian Diabetes Association recommend that patients with type 2 diabetes participate in aerobic exercise for at least 150 minutes per week, of which at least 90 minutes should be vigorous aerobic exercise. Both organizations also recommend these patients participate in resistance training at least three times per week, progressing to three sets of eight to 10 repetitions. Unger points out that it is best for patients with diabetes to exercise daily because that will decrease their insulin resistance.
That said, there is some good news to be gleaned from the study, according to Unger. He says he thinks it will encourage family physicians to recommend physical activity to their patients, but he cautions that it's important to let patients know they should start off slowly and work toward a goal of exercising 30 minutes per day, five days per week. Unger recommends checking these patients' blood sugar shortly before and 30 minutes after exercise and then sharing those findings with patients; this process can help demonstrate to them that exercise really does lower their blood sugar in hopes of motivating them to exercise more intensively.
Michael Orzechowski, M.D., a board-certified family physician practicing in Anchorage, Alaska, who has a certificate of added qualifications in sports medicine and a special interest in helping his patients learn to exercise regularly to enhance their overall health, (see related story, "FP Challenges His Patients to 'Walk the Talk'") calls the study a "nice real-world study showing the benefits of exercise" for patients with diabetes. Even if the added glycemic benefits of resistance training were due only to the increased duration of time spent exercising, he notes, such exercise also can benefit patients by strengthening their muscles. And, Orzechowski points out, "These were realistic people who were taking their medicine" while they exercised. Although exercise cannot necessarily replace antidiabetic medications, he says, it may enhance the drugs' effectiveness.
That said, there is some good news to be gleaned from the study, according to Unger. He says he thinks it will encourage family physicians to recommend physical activity to their patients, but he cautions that it's important to let patients know they should start off slowly and work toward a goal of exercising 30 minutes per day, five days per week. Unger recommends checking these patients' blood sugar shortly before and 30 minutes after exercise and then sharing those findings with patients; this process can help demonstrate to them that exercise really does lower their blood sugar in hopes of motivating them to exercise more intensively.
Michael Orzechowski, M.D., a board-certified family physician practicing in Anchorage, Alaska, who has a certificate of added qualifications in sports medicine and a special interest in helping his patients learn to exercise regularly to enhance their overall health, (see related story, "FP Challenges His Patients to 'Walk the Talk'") calls the study a "nice real-world study showing the benefits of exercise" for patients with diabetes. Even if the added glycemic benefits of resistance training were due only to the increased duration of time spent exercising, he notes, such exercise also can benefit patients by strengthening their muscles. And, Orzechowski points out, "These were realistic people who were taking their medicine" while they exercised. Although exercise cannot necessarily replace antidiabetic medications, he says, it may enhance the drugs' effectiveness.
