Fat and Muscle Indices Assessed by pQCT: Relationships With Physical Activity and Type 2 Diabetes Risk

The aim of this study was to compare and determine the repeatability of foreleg and forearm muscle and fat indices evaluated by the peripheral quantitative computed tomography (pQCT). Effects of habitual physical activity and associated health risk of type 2 diabetes were examined within the interrelations of intermuscular adipose tissue (IMAT) and muscle density. Eighty-two premenopausal women (mean age +/- standard deviation: 38.6 +/- 4.7 yr) underwent dual-energy X-ray absorptiometry scans and pQCT of foreleg and forearm scans to assess muscle and fat parameters. Physical activity status was based on 4-d self-reported log and pedometer step counts. Fat and muscle distribution between the foreleg and forearm were similar and highly correlated to total body adiposity. The pQCT device reliably measured muscle density in the foreleg and forearm; coefficients of variation were 0.8% and 2.1%, which was therefore used to reflect IMAT status. Muscle density was positively related to physical activity and negatively associated with markers of fat distribution and risk for type 2 diabetes. The pQCT is a novel, noninvasive tool to assess IMAT and muscle density in the foreleg and forearm. Additional research is necessary to understand the biology of IMAT and its relations with physical activity and potentially, with risks for cardiometabolic disease.