Skeletal muscle dysfunction (sarcopenia) is an under-recognized target organ complication of CKD with substantial adverse clinical consequences of disability, hospitalization, and death. Sarcopenia in this proposal is defined by impaired metabolism and physical function associated with decreased skeletal muscle mass or function. Skeletal muscle tissue relies on mitochondria to efficiently utilize oxygen to generate ATP. Impaired mitochondrial energetics is a central mechanism of sarcopenia in CKD. The investigators propose a series of studies designed to shed light on the pathophysiology of sarcopenia in persons with CKD not treated with dialysis. Investigators will conduct a randomized-controlled intervention trial of combined resistance training and aerobic exercise vs. health education to assess changes in skeletal muscle mitochondrial function, metabolism and physical function. Investigators hypothesize that exercise improves mitochondrial function and physical function in persons with CKD. If successful, these experiments will identify novel pathophysiologic mechanisms for CKD-associated sarcopenia. The proposed study will provide useful insight into benefits associated with exercise among patients with CKD and investigate mechanisms associated with improved metabolism, muscle function and physical function in population.