**4. Conclusions**

This chapter reviewed the possible mechanisms that are linked to sarcopenia. The etiology of sarcopenia is multifactorial, including a wide range of both intramuscular and extra muscular factors. This chapter focuses only on the intramuscular factors that include oxidative stress, inflammation, lack of vitamins, and hormones. Extra muscular factors include adult stem cells, extra cellular matrix (e.g., the function of matrix metaloproteinases), capillary bed, and neuronal activity.
