BACKGROUND: While current recommendations on exercise type and volume have strong experimental bases, there is no clear evidence from large-sized studies indicating whether increasing training intensity provides additional benefits to subjects with type 2 diabetes. OBJECTIVE: To compare the effects of moderate-to-high intensity (HI) versus low-to-moderate intensity (LI) training of equal energy cost, ie, exercise volume, on modifiable cardiovascular risk factors. DESIGN: Pre-specified sub-analysis of the Italian Diabetes and Exercise Study (IDES), a randomized multicenter prospective trial comparing a supervised exercise intervention with standard care for 12 months (2005 to 2006). SETTING: Twenty-two outpatient diabetes clinics across Italy. PATIENTS: Sedentary patients with type 2 diabetes assigned to twice-a-week supervised progressive aerobic and resistance training plus exercise counseling (n = 303). INTERVENTIONS: Subjects were randomized by center to LI (n = 142, 136 completed) or HI (n = 161, 152 completed) progressive aerobic and resistance training, ie, at 55% or 70% of predicted maximal oxygen consumption and at 60% or 80% of predicted 1-repetition maximum, respectively, of equal volume. Main Outcome Measure(s): Hemoglobin (Hb) A1c and other cardiovascular risk factors; 10-year coronary heart disease (CHD) risk scores. RESULTS: Volume of physical activity, both supervised and non-supervised, was similar in LI and HI participants. Compared with LI training, HI training produced only clinically marginal, though statistically significant, improvements in HbA1c (mean difference -0.17%, 95% confidence interval -0.44 to 0.10, p = 0.03), triglycerides (-0.12 mmol/l, -0.34 to 0.10, p = 0.02) and total cholesterol (-0.24 mmol/l, -0.46 to -0.01, p = 0.04), but not in other risk factors and CHD risk scores. However, intensity was not an independent predictor of reduction of any of these parameters. Adverse event rate was similar in HI and LI subjects. CONCLUSIONS: Data from the large IDES cohort indicate that, in low-fitness individuals such as sedentary subjects with type 2 diabetes, increasing exercise intensity is not harmful, but does not provide additional benefits on cardiovascular risk factors. TRIAL REGISTRATION: www.ISRCTN.org ISRCTN04252749.

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