Exercise and Type 2 Diabetes

This pronouncement was written for the American College of Sports Medicine by: Ann Albright, Ph.D., R.D. (Chairperson); Marion Franz, M.S., R.D., C.D.E.; Guyton Hornsby, Ph.D., C.D.E.; Andrea Kriska, Ph.D., FACSM; David Marrero, Ph.D.; Irma Ullrich, M.D.; and Larry S. Verity, Ph.D., FACSM. SUMMARY Physical activity, including appropriate endurance and resistance training, is a major therapeutic modality for type 2 diabetes. Unfortunately, too often physical activity is an underutilized therapy. Favorable changes in glucose tolerance and insulin sensitivity usually deteriorate within 72 h of the last exercise session; consequently, regular physical activity is imperative to sustain glucose-lowering effects and improved insulin sensitivity. Individuals with type 2 diabetes should strive to achieve a minimum cumulative total of 1000 kcal·wk−1 from physical activities. Those with type 2 diabetes generally have a lower level of fitness (V̇O2max) than nondiabetic individuals, and therefore exercise intensity should be at a comfortable level (RPE 10–12) in the initial periods of training and should progress cautiously as tolerance for activity improves. Resistance training has the potential to improve muscle strength and endurance, enhance flexibility and body composition, decrease risk factors for cardiovascular disease, and result in improved glucose tolerance and insulin sensitivity. Modifications to exercise type and/or intensity may be necessary for those who have complications of diabetes. Individuals with type 2 diabetes may develop autonomic neuropathy, which affects the heart rate response to exercise, and as a result, ratings of perceived exertion rather than heart rate may need to be used for moderating intensity of physical activity. Although walking may be the most convenient low-impact mode, some persons, because of peripheral neuropathy and/or foot problems, may need to do non-weight-bearing activities. Outcome expectations may contribute significantly to motivation to begin and maintain an exercise program. Interventions designed to encourage adoption of an exercise regimen must be responsive to the individual’s current stage of readiness and focus efforts on moving the individual through the various “stages of change.” INTRODUCTION Diabetes is one of the leading causes of death and disability in the United States with type 2 diabetes accounting for 90–95% of all diabetic cases (77). Based on national data, there are about 10.3 million diagnosed cases of diabetes in the United States with an estimated 5.4 million additional undiagnosed cases in the general population (40). Unfortunately, the diagnosis of type 2 diabetes is often delayed for years after the onset of the disease. A large portion of the burden of the disease falls upon the minority populations of the U.S., demonstrated by the fact that the prevalence rates of diabetes are higher among Native Americans, African Americans, Hispanic Americans, and Asian and Pacific Island Americans when compared with non-Hispanic whites (99). The long-term complications associated with type 2 diabetes are both microvascular and macrovascular in nature and include the following: retinopathy, peripheral and autonomic neuropathy, nephropathy, peripheral vascular disease, atherosclerotic cardiovascular and cerebrovascular disease, hypertension, and susceptibility to infections and periodontal disease (for an extensive description of the complications associated with diabetes, the reader is referred to Diabetes in America, 1995; 80,81). The diagnosis and classification of diabetes have been revised by the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus (59). The new classification system emphasizes etiology and pathogenesis rather than modalities of treatment. 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