A decline in mitochondrial biogenesis and mitochondrial protein quality control in skeletal muscle is a common finding in aging, but exercise training has been suggested as a possible cure. In this report, we tested the hypothesis that moderate-intensity exercise training could prevent the age-associated deterioration in mitochondrial biogenesis in the gastrocnemius muscle of Wistar rats. Exercise training, consisting of treadmill running at 60% of the initial Vo(2max), reversed or attenuated significant age-associated (detrimental) declines in mitochondrial mass (succinate dehydrogenase, citrate synthase, cytochrome-c oxidase-4, mtDNA), SIRT1 activity, AMPK, pAMPK, and peroxisome proliferator-activated receptor gamma coactivator 1-α, UCP3, and the Lon protease. Exercise training also decreased the gap between young and old animals in other measured parameters, including nuclear respiratory factor 1, mitochondrial transcription factor A, fission-1, mitofusin-1, and polynucleotide phosphorylase levels. We conclude that exercise training can help minimize detrimental skeletal muscle aging deficits by improving mitochondrial protein quality control and biogenesis.