A comparison of methods for analyzing glucose and insulin areas under the curve following nine months of exercise in overweight adults

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Abstract
OBJECTIVE: We examined three methods for calculating the area under the curve (AUC) following an oral glucose tolerance test (OGTT) in overweight adults prior to and after 9 months of exercise. METHOD: Subjects (n=27) were randomly assigned to a control (CON, n=9) or intervention (INT, n=18) group. INT performed supervised exercise 5 days per week, 45 min per session, at 65% of heart rate reserve. OGTTs were administered pre- and post-training. Blood was collected during a 75 g OGTT and analyzed for glucose (GLU) and insulin (INS) concentrations. AUCs were calculated using the incremental, positive incremental, and total AUC methods and the difference scores for pre- and post-training were determined. RESULTS: No differences were observed among the methods for glucose AUC for either group. Significant differences were observed for INT insulin AUC with total AUC (1525±3291 µU/1/180 min) significantly greater than incremental AUC (1112±3229 µU/1/180 min) or positive incremental AUC (1085±3195 µU/I/180 min). Total insulin AUC was significantly reduced following training for INT, while incremental and positive incremental insulin AUCs showed no change. CONCLUSION: These data suggest that the method of used to calculate AUC may affect the interpretation of whether or not an intervention was effective.