Effects of aerobic and resistance training on hemoglobin A1c levels in patients with type 2 diabetes: a randomized controlled trial

Abstract

Context: Exercise guidelines for individuals with diabetes include both aerobic and resistance training although few studies have directly examined this exercise combination.

Objective: To examine the benefits of aerobic training alone, resistance training alone, and a combination of both on hemoglobin A(1c) (HbA(1c)) in individuals with type 2 diabetes.

Design, setting, and participants: A randomized controlled trial in which 262 sedentary men and women in Louisiana with type 2 diabetes and HbA(1c) levels of 6.5% or higher were enrolled in the 9-month exercise program between April 2007 and August 2009.

Intervention: Forty-one participants were assigned to the nonexercise control group, 73 to resistance training 3 days a week, 72 to aerobic exercise in which they expended 12 kcal/kg per week; and 76 to combined aerobic and resistance training in which they expended 10 kcal/kg per week and engaged in resistance training twice a week. Main Outcome Change in HbA(1c) level. Secondary outcomes included measures of anthropometry and fitness.

Results: The study included 63.0% women and 47.3% nonwhite participants who were a mean (SD) age of 55.8 years (8.7 years) with a baseline HbA(1c) level of 7.7% (1.0%). Compared with the control group, the absolute mean change in HbA(1c) in the combination training exercise group was -0.34% (95% confidence interval [CI], -0.64% to -0.03%; P = .03). The mean changes in HbA(1c) were not statistically significant in either the resistance training (-0.16%; 95% CI, -0.46% to 0.15%; P = .32) or the aerobic (-0.24%; 95% CI, -0.55% to 0.07%; P = .14) groups compared with the control group. Only the combination exercise group improved maximum oxygen consumption (mean, 1.0 mL/kg per min; 95% CI, 0.5-1.5, P < .05) compared with the control group. All exercise groups reduced waist circumference from -1.9 to -2.8 cm compared with the control group. The resistance training group lost a mean of -1.4 kg fat mass (95% CI, -2.0 to -0.7 kg; P < .05) and combination training group lost a mean of -1.7 (-2.3 to -1.1 kg; P < .05) compared with the control group.

Conclusions: Among patients with type 2 diabetes mellitus, a combination of aerobic and resistance training compared with the nonexercise control group improved HbA(1c) levels. This was not achieved by aerobic or resistance training alone.

Trial registration: clinicaltrials.gov Identifier: NCT00458133.

Figure 1. Participant Flow Chart

Figure 2

Monthly Hemoglobin A_1c Levels Monthly mean hemoglobin A_1c (HbA_1c) levels, derived from a mixed-linear model containing the covariates of age, sex, race/ethnicity, diabetes duration, and baseline HbA_1c, are presented for group with the intention-to-treat analysis (n=262) and the per-protocol analysis (n = 215). For the intention-to-treat model, the group (P=.01) and month (P< .001) effect were statistically significant. Error bars represent standard errors.