The HART-D trial showed that people with diabetes should mix aerobics with weight training to get the best results in lowering blood sugar and also worked best for weight loss….
Timothy Church, MD, PhD, of Pennington Biomedical Research Center in Baton Rouge, La., reported that the significant reduction of 0.34% through nine months of training was not achieved by either type of exercise on its own.
In an accompanying editorial Ronald Sigal, MD, MPH, of the University of Calgary in Alberta, and Glen Kenny, PhD, of the University of Ottawa, wrote, “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.”
Although exercise guidelines for patients with diabetes include both aerobic and resistance training, few studies have evaluated the relative merits of each type of exercise alone and in combination.
Church and his colleagues explored the issue in the nine-month HART-D (Health Benefits of Aerobic and Resistance Training in Individuals with Type 2 Diabetes) study, which included 262 sedentary men and women in Louisiana with Type 2 diabetes and hemoglobin A1c levels of 6.5% or higher (mean 7.7%).
The participants were assigned to one of four groups:
- Non-exercise control (41 patients)
- Resistance training alone (73 patients)
- Aerobic exercise alone (72 patients)
- Combined resistance and aerobic training (76 patients)
Aerobic exercise included walking on a treadmill with the goal of expending 12 kcal/kg per week. Resistance training included sessions three days per week with upper body, leg, abdomen, and back exercises. The combination training program included only two days of resistance training per week to keep the total exercise time consistent in all three groups.
During the study, participants in each of the three intervention groups spent about 140 minutes exercising each week under supervision, including warm-up and cool-down time.
Through nine months, the average A1c level increased by 0.11% in the control group, but declined in each of the three exercise groups.
Compared with the control group, however, the absolute reduction in A1c level was significant only in the combination training group (-0.34%, P=0.03).
Such a reduction might be expected to reduce cardiovascular disease risk by 5% to 7% and microvascular complications by 12%, according to the researchers.
“However, these risk reduction estimates are likely conservative because they are derived from medication studies and do not take into account improvements in cardiorespiratory fitness and strength and reductions in fat mass and waist circumference,” they wrote.
All three of the exercise groups shaved 1.5 to 2.8 cm from their waists. Fat mass was reduced by 3 pounds in the resistance training group and 3.7 pounds in the combination training group (P<0.05 for both).
Only participants in the combination group were significantly more likely than those in the control group to meet a composite endpoint of decreasing hypoglycemic medications or reducing A1c level by 0.5% without increasing medications (41% versus 22%; OR 2.9, 95% CI 1.2 to 7.0).
According to Sigal and Kenny, the results add to the findings from an earlier study, the Diabetes Aerobic and Resistance Exercise (DARE) trial, which also suggested that combined training was more effective than either type of exercise alone for glycemic control.
They also noted that, “Changes achieved in the HART-D trial were modest, perhaps because there was no effort to minimize medication changes. Participants whose A1c level did not improve with exercise were more likely to have their hypoglycemic therapy intensified, thus attenuating the difference in A1c.”
Both trials used supervised exercise programs, which represents a limitation in terms of disseminating such programs.
The results obtained in these trials may be better than what can be expected if patients attempt these interventions at home, because prior studies of home-based resistance training did not demonstrate improved glycemic control.
“This is a common theme for lifestyle interventions. Obesity is indeed treatable if supervised diet and exercise programs are provided at no cost to patients, whereas these types of interventions appear to be less successful when implemented by patients by themselves.”
- Point out that this study suggests that combining resistance and aerobic training has more beneficial effects than using either one alone, with the same amount of time spent in exercising.
Church T, et al “Effects of aerobic and resistance training on hemoglobin A1c levels in patients with Type 2 diabetes” JAMA Nov. 24, 2010; 304: 2253-2262.