Exercise Reduces HbA1c in Type 2 Diabetics, but Improved Strength Associates with Poorer Outcomes

More than 25 million Americans have type 2 diabetes. Exercise is an effective method to prevent, delay, or manage the disease; however, fewer than 40% of patients report engagement in physical activity and more than 20% of this group overestimate their engagement. Structured exercise is warranted. Both aerobic and resistance training may be more effective than either mode in isolation, but studies reporting this are limited by their combined groups having greater volumes of exercise. PURPOSE: To evaluate different volumes of combined aerobic and resistance exercise on HbA1c levels in adults with diabetes. METHODS: 67 patients were randomly assigned to one of two groups: Group 1 performed supervised aerobic and resistance exercise twice per week. Group 2 performed the same exercise as Group 1 but also walked for 60 min on two additional days. At baseline, health history, seven tests of physical functioning, and measured cardiometabolic parameters, including HbA1c was performed. Following 10 weeks of exercise, follow-up data were collected. Independent-samples t tests compared baseline data and rates of improvement between the two groups. Multiple linear regression tested predictors of improvement in HbA1c. RESULTS: Group differences at baseline were minimal. Patients in Group 2 were 4.7 years older (p=0.063), body mass index was 3.3 points lower (p=0.058), and they walked an additional 72.7 meters in the 6-minute walk (p=0.009). There were no differences in body fat percent (p=0.507), HbA1c (p=0.512), other cardiometabolic parameters, or the other six assessments of physical functioning. The patients who completed the exercise intervention improved in 13 of 15 assessments (p\u3c0.05), including HbA1c (p=0.045). There were no differences in improvement between exercise groups. Regression analysis found elevated baseline body fat percent (p=0.001) and improvements in strength, assessed by arm curls (p=0.009) and grip strength (p=0.042) to correspond to poorer outcomes in HbA1c; the overall model was significant (R2=0.733; p\u3c0.001). CONCLUSIONS: Ten weeks of combined aerobic and resistance exercise improved cardiometabolic profiles of diabetic patients, including HbA1c. Additional volume of aerobic exercise did not enhance outcomes and improvements in strength associated with poorer outcomes