Subjects: Behavioral health
Scientists have known for years that people with type 2 diabetes can benefit from exercise, although the precise roles played by aerobic exercise and resistance training have been somewhat of a mystery. Until now, that is.
In a paper published last month in JAMA, Timothy Church and colleagues from LSU showed that type 2 diabetes patients benefit more from an exercise regimen that combines the 2 forms of exercise than programs based on either one, alone.
To assess the relative effects of aerobic training and resistance training, Church’s group studied 262 sedentary male and female patients that had type 2 diabetes. In the 9-month study, dubbed HART-D, the average age of the patients was 56. They had diabetes for an average of 7 years. Their average HbA1c level was 7.7%, indicating moderately well controlled diabetes at study onset. Nearly half the patients were not Caucasian.
The scientists randomized enrollees into a non-exercise control group, a resistance training only group, an aerobic training only group, and a group that underwent combined aerobic and resistance training.
Participants in the 3 intervention groups spent about 140 minutes in supervised exercise per week, including time spent warming-up and cooling-down. Aerobic exercise involved walking fast enough on a treadmill to burn 12 kcal/kg per hour. Resistance training was divided into 3 sessions per week, and focused on the upper body, legs, abs and back. Participants in the combination training program engaged in resistance training only twice per week in order to keep total exercise time the same as the other groups.
The scientists found that the absolute change in HbA1c in the combination group compared to the control group was -0.34%. This compared favorably with an absolute change of -0.16% and -0.24% for the resistance only and the aerobic only groups.
Church’s group estimated that if such reductions were maintained for years, people with type 2 diabetes would reduce the risk of cardiovascular disease risk by 5% to 7% and the risk of microvascular complications by 12%.
Of great significance, Church’s group also noted that the frequency with which oral hypoglycemic drugs had to be increased was 18% in the combination group. This was significantly lower than the 22% for the aerobic training only group, 32% for the resistance training only group, and 39% in the controls. Without these aggressive interventions, the absolute improvements in HbA1c levels in the combined exercise group would almost certainly have been much greater, according to the scientists.
All exercise groups reduced waist circumference by about the same amount [-.75 to -1.1 inches] when compared to the control group.
In an accompanying editorial, Canadian researchers, Ronald Sigal and Glen Kenny concluded that, “based on the results of the HART-D trial, patients with type 2 diabetes who wish to maximize the effects of exercise on their glycemic control should perform both aerobic and resistance exercise. The HART-D trial clarifies that, given a specific amount of time to invest in exercise, it is more beneficial to devote some time to each form of exercise rather than devoting all the time to just one form of exercise.”
One note of caution: Although this is clearly good news, the study may not be easily generalizable to the population at large because the study design required that all exercise sessions be supervised. It turns out that without that pesky trainer and the forced adherence to an exercise regimen, many folks, whether they have diabetes or not, can’t manage to stick with an exercise plan.