Moderate Exercise of 120 Minutes per Week Improves Aerobic Fitness and Waist Circumference but Not Insulin Sensitivity in Persons with Elevated Fasting Glucose

Aim. As the vast majority of those at risk for type 2 diabetes mellitus (T2DM) fail to meet the recommended 150 minutes of moderate physical activity per week, the primary purpose of this study was to determine whether an exercise program consisting of a total of 120 min of moderate-intensity exercise/week would improve insulin sensitivity in persons with impaired glucose tolerance. Methods. The effect of an 8-wk program of treadmill walking (4 sessions per week of 30 min duration at 40-60% of heart rate reserve) on insulin resistance was determined in a sample of sedentary adults (N.=29, 43.6 ± 11.15 yr) with a fasting glucose between 95 - 125 mg/dL (102.2 ± 10.91 mg /dL). Fasting insulin and glucose and fasting indices of insulin sensitivity were determined. Oral glucose tolerance tests data were used in several quantitative insulin sensitivity models. Blood lipids, blood pressure, aerobic capacity and anthropometric data were also collected before and after the exercise intervention. Results. Training resulted in a reduction in waist circumference and an increase in estimated aerobic capacity but no change in any measures of insulin sensitivity. Conclusion. Several published studies in normoglycemic subjects have reported significant improvements in markers of insulin sensitivity with exercise of similar volume and intensity to that of the current investigation. The results of this study suggest that the threshold dose and/or the intensity of exercise necessary to improve clinical markers of insulin sensitivity in those with impaired glucose tolerance may be higher than that required for normoglycemic subjects