Physical Activity, Cardiorespiratory Fitness, and the Diabetes Spectrum

Physical activity and cardiorespiratory fitness greatly impact the diabetic spectrum of disorders such as prediabetes, gestational diabetes, and type 1 and type 2 diabetes. Epidemiologically, there is a strong and inverse association between fitness status and diabetes incidence. Randomized controlled trials have also shown that diabetes incidence is significantly reduced in individuals with prediabetes when a lifestyle intervention program is implemented and cardiorespiratory fitness improves. Although improvement in microvascular disease in these intervention trials has not been shown, mortality is decreased. Subjects with both DM1 and DM2 have reduced cardiorespiratory fitness. In those with early DM2, fitness strongly improves glycemic parameters in a dose-dependent manner to cardiorespiratory fitness. In more established diabetes, although the emphasis historically has been on the volume of the aerobic component of exercise, there is a bourgeoning additive benefit role for resistance training, and the consensus guidelines recommend a combination of aerobic and resistance activity as well as minimizing inactivity along with nutritional support. The role of high-intensity interval training, for those medically capable, has also been shown to increase cardiorespiratory fitness benefit with reduced investment in time.