During aging, there is a gradual decrease in the ability to maintain skeletal muscle function and mass. This condition is called sarcopenia , and may be distinct from atrophy in its pathophysiology. While the exact cause of sarcopenia is unknown, it may be induced by a combination of a gradual failure in the satellite cells which help to regenerate skeletal muscle fibers, and a decrease in sensitivity to or the availability of critical secreted growth factors which are necessary to maintain muscle mass and satellite cell survival. 
There is also some crosstalk with the H 2 S signalling pathway and the nitric oxide pathway, since H 2 S can degrade the molecule known as S-nitrosoglutathione,  which serves as an intracellular (and to a degree, extracellular  ) reservoir of nitric oxide that garlic is known to stimulate.  Due to this, the influence of garlic on blood pressure and blood flow is in part due to nitric oxide signalling per se (the vasorelaxing effect of opening potassium channels to be discussed in the ion channels section  ) and in part an influence of the hydrogen sulfide system unto the nitric oxide system.