Performing a combination of aerobic exercise and resistance training was associated with improved glycemic levels among patients with type 2 diabetes, compared to patients who did not exercise, according to a study in the November 24 issue of Journal of the American Medical Association. The level of improvement was not seen among patients who performed either aerobic exercise or resistance training alone. Although it is unanimously accepted that regular exercise provides substantial health benefits for individuals with type 2 diabetes, the exact exercise type (aerobic vs. resistance vs. both) has been unclear. “Given that the 2008 Federal Physical Activity Guidelines recommend aerobic exercise in combination with resistance training, the unanswered question as to whether for a given amount of time the combination of aerobic and resistance exercise is better than either alone has significant clinical and public health importance,” the authors write.

Timothy S. Church, MD, MPH, of Louisiana State University and colleagues conducted the HART-D trial, which compared among 262 sedentary women and men with type 2 diabetes the effect of aerobic training, resistance training, and a combination of both on change in hemoglobin A1c levels (HbA1c). HbA1c is a minor component of hemoglobin - the part of red blood cells that carries oxygen to the cells - and to which glucose is bound. (HbA1c levels are used to monitor the control of diabetes mellitus). The individuals were enrolled in the 9-month exercise program between April 2007 and August 2009. Forty-one participants were assigned to the non-exercise control group; 73 to resistance training sessions; 72 to aerobic exercise sessions; and 76 to combined aerobic and resistance training.

The researchers found that the absolute change in HbA1c in the combination training group vs. the control group was -0.34 percent. The resistance training group posted an average change of -0.16 percent, and the aerobic group a change of -0.24 percent. By far, the combined group saw the most significant change in HbA1c compared with those in the control group. Over the course of the exercise program, medication usage to manage blood sugar increased by 39 percent in the control group, 32 percent in the resistance training, 22 percent in the aerobic, and 18 percent in the combination training groups.

“The primary finding from this randomized, controlled exercise trial involving individuals with type 2 diabetes is that although both resistance and aerobic training provide benefits, only the combination of the two were associated with reductions in HbA1c levels,” the researchers write. “It also is important to appreciate that the follow-up difference in HbA1c between the combination training group and the control group occurred even though the control group had increased its use of diabetes medications while the combination training group decreased its diabetes medication uses.”

Ronald J. Sigal, MD, MPH, of the University of Calgary in Alberta, and Glen P. Kenny, Ph.D., of the University of Ottawa and Ottawa Hospital Research Institute, Ottawa, write in an accompanying editorial that this study provides important evidence on the effects of aerobic and resistance training on improving hemoglobin HbA1c levels. “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. [This] clarifies that, given a specific amount of time to invest…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.”

Reference:

Church, TS, et al. (2010). Effects of Aerobic and Resistance Training on Hemoglobin A1c Levels in Patients With Type 2 Diabetes. Journal of the American Medical Association, 304(20), pp. 2253-2262.