Eligibility, Screening and Testing. Following IRB approval, a study coordinator will send an invitation letter describing the study to eligible participants previously identified via fasting glucose levels as pre-diabetic. Interested participants will be contacted by the study coordinator for further eligibility screening. Exercise testing will take place at the School of Nursing Exercise Physiology Laboratory. After an overnight fast, participants will arrive in the morning at the Clinical Research Unit to have blood samples collected for Metabolomics, A1C, glucose and insulin, receive cognitive testing, and magnetic resonance imaging (MRI). Participants will undergo MRI at the Wisconsin Institutes for Medical Research (WIMR).