Aerobic physical activity is a major therapeutic modality for type 2 diabetes (1,2). It is well known that regular aerobic exercise produces beneficial effects on glycemic control, insulin sensitivity, lipid abnormalities, and hypertension (3,4). On the other hand, several recent studies (5,6) have demonstrated the beneficial effect of resistance exercise in diabetes, and these results should encourage its practice because of the increasing number of sedentary, older, and obese people in industrialized countries. In fact, this is particularly important in the case of individuals who may be noncompliant with aerobic exercise. To prove the effectiveness of resistance training, a recent study (7) showed the positive effects of prescribed and supervised high-intensity resistance training for 16 weeks in high-risk older adults with type 2 diabetes, resulting in improved glycemic and metabolic control. Similarly, 16 weeks of resistance plus aerobic training is reported to enhance glucose disposal in postmenopausal women with type 2 diabetes (8). Both of these studies evaluate the effect of relatively short-period physical training but neither investigates prolonged resistance exercise combined with aerobic training in diabetic people.
We therefore investigated the long-term effects (1 year) of prescribed and supervised combined aerobic and resistance training on glycemic control, cardiovascular risk factors, and body composition in type 2 diabetic patients.
Physical examination was performed to detect the presence and degree of complications as well as to determine any orthopedic limitations. After selection, 120 (60 men and 60 women) sedentary type 2 diabetic patients, aged 60.9 ± 8.9 years, with duration of diabetes 9.8 ± 7.3 years, were included in the study and randomly assigned to one of two treatments: 62 subjects (30 men and 32 women) agreed to perform the aerobic plus resistance training (ART) program, whereas 58 subjects (30 men and 28 women) asked to continue with their current diet and pharmacological therapy and formed the control group. The subjects in both groups continued to receive their standard medication. Throughout the study, diabetologists were asked to avoid nonessen-tial changes in drugs and dosages that might affect the study outcome measures. Every essential medication change was implemented and then reported to the investigators.
The ART group performed 30 min of aerobic training at 40–80% of the heart rate reserve (based on the initial maximal graded exercise tolerance test) using treadmills, stationary bicycles, reclining bicycles, and elliptical trainers (Technogym), plus another 30-min resistance training program that included free weights, such as barbells or dumbbells, and weight machines at 40–60% of a single repetition maximal lift (1 RM), which was retested every 3 weeks. The workload was 12 repetitions each of six exercises selected for each major muscle group (i.e., legs, chest, shoulders, back, arms, and abdomen) for three sets, three times a week, for 1 year.
Blood pressure and plasma glucose levels were assessed in each patient by means of a One Touch Ultra blood glucose monitoring system (Lifescan) before and after each training setting. HbA1c, BMI, waist circumference, and glycemic and lipid profiles were evaluated every 3 months. Each participant was provided with written handouts and with a notebook in which to take notes and record food diaries. A 3-day food record was obtained at baseline and every 3 months for 1 year. All nutritional information obtained from food records was analyzed by a dietitian using Winfood software (Medimatica). Body composition was measured at baseline and after 1 year by means of dual-energy X-ray absorptiometry (QDR 1000; Hologic).
This study was conducted in accordance with the Declaration of Helsinki guidelines. Each subject gave his or her informed consent before the study began.
Each group was compared using the ANOVA test with multiple comparisons and 95% CIs. A two-tailed P < 0.05 indicated statistical significance. All of the values are expressed as means ± SD. Subjects in the ART group attended >90% of the prescribed program sessions. The subject dropout rates were 17.7% for the ART group and 8.63% for the control group. We only included patients who completed the entire year for statistical analyses.
There were no significant differences between the two groups at baseline with respect to BMI (30 ± 5.6 vs. 30.1 ± 5.6 kg/m2), fat mass (33 ± 9.2 vs. 35 ± 10.2%), fat-free mass (48.1 ± 10 vs. 46.8 ± 11 kg), waist circumference (104 ± 12.8 vs. 103 ± 14 cm), fasting blood glucose (163 ± 59.6 vs. 165 ± 60.6 mg/dl), total cholesterol (212 ± 31.5 vs. 212 ± 40.2 mg/dl), HDL cholesterol (45.3 ± 9.8 vs. 43.6 ± 9.1 mg/dl), LDL cholesterol (134 ± 31.6 vs. 130 ± 34.2 mg/dl), triglycerides (159 ± 80.1 vs. 187 ± 109 mg/dl), HbA1c (8.28 ± 1.73 vs. 8.31 ± 1.73%), systolic blood pressure (147 ± 18 vs. 139 ± 17.1 mmHg), diastolic blood pressure (85.6 ± 7.8 vs. 85.3 ± 8.8 mmHg), and use of lipid-lowering, hypoglycemic, and antihypertensive medications (32.3 vs. 34.5, 80.8 vs. 86.3, and 48.4 vs. 50%, respectively).
After 1 year, the control group showed no statistically significant change in any measured parameters. The ART group, conversely, showed a statistically significant decrease in BMI (30.1 ± 5.6 to 28.8 ± 4.8 kg/m2, P < 0.0001), fat mass (35 ± 10.2 to 32.5 ± 10.2%, P < 0.0001), waist circumference (103 ± 14 to 98 ± 12.7 cm, P < 0.0001), fasting blood glucose (165 ± 60.6 to 129 ± 37 mg/dl, P < 0.0001), total cholesterol (212 ± 40.2 to 195 ± 35.4 mg/dl, P < 0.0001), LDL cholesterol (130 ± 34.2 to 124 ± 28.7 mg/dl, P < 0.0001), triglycerides (187 ± 109 to 146 ± 81 mg/dl, P < 0.0001), HbA1c (8.31 ± 1.73 to 7.1 ± 1.16%, P < 0.0001), systolic blood pressure (139 ± 17.1 to 135 ± 15.5 mmHg, P < 0.04), and diastolic blood pressure (85.3 ± 8.8 to 81.3 ± 6.7 mmHg, P < 0.0001) and a significant increase in fat-free mass (46.8 ± 11 to 47.2 ± 10.8 kg, P < 0.0001) and HDL cholesterol (43.6 ± 9.1 to 48.6 ± 12.1 mg/dl, P < 0.0001).
The frequency of medication changes was not significantly different between the ART and control groups. We observed a trend toward decreasing amounts of medications in all three classes of drugs (hypolipemic, hypoglycemic, and antihypertensive therapies) in the ART group (−7.85, −3.94, and −5.90%, respectively), whereas in the control group, the opposite trend occurred (5.67, 7.55, and 5.67%, respectively).
Throughout the entire study, no adverse effects occurred in any patient. The reasonably low dropout rate in the ART group (17.7%) indicates that subjects with type 2 diabetes are willing and able to participate in a demanding intervention program if it is made available to them.
In conclusion, the combination of aerobic and resistance training is well tolerated, feasible, and safe, and it improves glycemic control, cardiovascular risk factors, and body composition in type 2 diabetic patients. Given the epidemic of diabetes and metabolic syndrome in the recent years, we stress the use of combined exercise as an adjunct to standard medical care in the management of these patients.