In patients with type 2 diabetes mellitus, aerobic exercise combined with resistance training improves glycosylated hemoglobin (HbA1c) levels vs levels in a nonexercising control group; however, neither form of exercise alone achieves this benefit, a new study has found.
Timothy S. Church, MD, PhD, with the Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, and colleagues reported the findings in the November 24 issue of the Journal of the American Medical Association.
According to the researchers, it is known that exercise benefits patients with type 2 diabetes, but “the exact exercise prescription in terms of type (aerobic vs resistance vs both) is unclear.”
To elucidate the relative contribution of aerobic and strength training, the researchers conducted a randomized controlled trial including 262 sedentary participants with type 2 diabetes and HbA1c levels of 6.5% or higher. Participants were enrolled in a 9-month exercise program between April 2007 and August 2009.
A total of 41 subjects were assigned to the nonexercise control group. The remaining participants were assigned to resistance training 3 days a week; aerobic exercise (12 kcal/kg per week of energy expenditure); or combined aerobic and resistance training (10 kcal/kg per week of energy expenditure), in addition to resistance training twice a week.
Levels of HbA1c decreased by an average of 0.34% (95% confidence interval [CI], −0.64% to −0.03%; P = .03) in the combined group, whereas there was no significant decline in either the aerobic training-alone group or the strength training-alone group vs the nonexercising control group.
The combination exercise group had an improved maximal oxygen consumption (mean, 1.0 mL/kg/minute; 95% CI, 0.5 – 1.5; P < .05) vs the control group. In addition, during the 9-month study, all exercise groups had a decrease in waist circumference from −1.9 to −2.8 cm vs the control group.
The resistance training group also lost a mean of −1.4 kg of fat mass (95% CI, −2.0 to −0.7 kg; P < .05), and the combined group lost a mean of −1.7 kg of fat mass (95% CI, −2.3 to −1.1 kg; P < .05) vs the control group. The decline in fat mass in the aerobic training group was not significant, however.
“…although both resistance and aerobic training provide benefits, only the combination of the 2 were associated with reductions in HbA1c levels,” the study authors conclude. “Furthermore, cumulative benefit across all outcomes was greater in the combination training group compared with either aerobic or resistance training alone,” they add.
The researchers note that this is the “first large randomized trial involving individuals with type 2 diabetes to directly test exercise prescriptions that are consistent with the 2008 Physical Activity Guidelines of 500 to 1000 MET [metabolic equivalent tasks] minutes per week combined with 2 days of resistance training.”
In a related editorial, Ronald J. Sigal, MD, MPH, and Glen P. Kenny, PhD, with the University of Ottawa and Ottawa Hospital Research Institute, in Ontario, Canada, noted that the study results add to the results of other studies that also suggest that “combined aerobic and resistance exercise was more effective than either type of exercise alone for improvement of glycemic control in type 2 diabetes.”
“…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,” they add.