The mechanisms accounting for the loss of muscle function with obesity and type 2 diabetes are likely the result of a combination of neural and muscular factors. One muscular factor that is important, yet has received little attention, is the protein machinery involved in longitudinal and lateral force transmission. The purpose of this study was to compare the levels of force transfer and membrane integrity proteins before and after a 12-week endurance training program in lean, obese, and obese type 2 diabetic adults. Nineteen sedentary subjects (male = 8 and female = 11) were divided into three groups: Lean (n = 7; 50.3 +/- 4.1 y; 69.1 +/- 7.2 kg); Obese (n = 6; 49.8 +/- 4.1 y; 92.9 +/- 19.5 kg); and Obese with type 2 diabetes (n = 6; 51.5 +/- 7.9 years; 88.9 +/- 15.1 kg). Participants trained 150 min/week between 55% and 75% of VO2max for 12 weeks. Skeletal muscle biopsies were taken before and after the training intervention. Baseline dystrophin and muscle LIM protein levels were higher (similar to 50% p < .01) in lean compared to obese and type 2 diabetic adults, while the protein levels of the remaining force transfer and membrane integrity proteins were similar between groups. After training, obese individuals decreased (-53%; p < .01) the levels of the muscle ankyrin repeat protein and lean individuals decreased dystrophin levels (-45%; p = .01), while the levels of the remaining force transfer and membrane integrity proteins were not affected by training. These results suggest that there are modest changes to force transfer and membrane integrity proteins in middle-aged individuals as a result of 12 weeks of lifestyle and training interventions.