It is used principally in combination with other tonic herbs, as a strengthening, "warming" tonic herb alleged to rejuvenate and revitalize the body. In Asia, ginseng is used for a variety of functions, primarily to boost energy levels and alertness in older persons. It is also used to enhance resiliency and balance metabolism in the face of stress. It is also used to strengthen the sexual system, improve athletic performance and endurance, gently stimulate the nervous system, and enhance memory and concentration.