The tumoricidal capacity of the NKs is enhanced in vitro by certain interleukins, especially IL-2. The in vivo activity of the NKs is not yet fully known, but it has been observed that patients with low NK count are more susceptible to certain types of tumors, for example certain types of lymphomas. It is currently used in humans of IL-2 as a therapy against tumors, especially in kidney cancer.
Specificity is the answer. You are targeting a certain muscle in your body to improve it for an upcoming sport or activity like running a marathon or entering a Mr.Olympian body-building competition.
